--- loncom/interface/statistics/lonproblemstatistics.pm	2002/08/02 21:04:46	1.11
+++ loncom/interface/statistics/lonproblemstatistics.pm	2006/12/06 22:22:38	1.111
@@ -1,7 +1,6 @@
 # The LearningOnline Network with CAPA
-# (Publication Handler
 #
-# $Id: lonproblemstatistics.pm,v 1.11 2002/08/02 21:04:46 minaeibi Exp $
+# $Id: lonproblemstatistics.pm,v 1.111 2006/12/06 22:22:38 albertel Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -26,861 +25,1783 @@
 # http://www.lon-capa.org/
 #
 # (Navigate problems for statistical reports
-# YEAR=2001
-# 5/5,7/9,7/25/1,8/11,9/13,9/26,10/5,10/9,10/22,10/26 Behrouz Minaei
-# 11/1,11/4,11/16,12/14,12/16,12/18,12/20,12/31 Behrouz Minaei
-# YEAR=2002
-# 1/22,2/1,2/6,2/25,3/2,3/6,3/17,3/21,3/22,3/26,4/7,5/6 Behrouz Minaei
-# 5/12,5/14,5/15,5/19,5/26,7/16,7/25,7/29  Behrouz Minaei
 #
-###
+###############################################
+###############################################
 
-package Apache::lonproblemstatistics; 
+=pod
+
+=head1 NAME
+
+lonproblemstatistics
+
+=head1 SYNOPSIS
+
+Routines to present problem statistics to instructors via tables,
+Excel files, and plots.
+
+=over 4
+
+=cut
+
+###############################################
+###############################################
+
+package Apache::lonproblemstatistics;
 
 use strict;
-use Apache::lonnet();
+use Apache::lonnet;
+use Apache::loncommon();
 use Apache::lonhtmlcommon;
 use Apache::loncoursedata;
-use GDBM_File;
+use Apache::lonstatistics;
+use LONCAPA::lonmetadata();
+use Apache::lonlocal;
+use Spreadsheet::WriteExcel;
+use Apache::lonstathelpers();
+use Time::HiRes;
+use LONCAPA;
+ 
 
+my @StatsArray;
+my %SeqStat;    # keys are symbs, values are hash refs
 
-sub BuildProblemStatisticsPage {
-    my ($cacheDB, $students, $courseID, $c, $r)=@_;
-    my %cache;
-    #my %DoDiff;
-    unless(tie(%cache,'GDBM_File',$cacheDB,&GDBM_READER,0640)) {
-        return '<html><body>Unable to tie database.</body></html>';
-    }
-
-    my $Ptr = '';
-    $Ptr .= '<table border="0"><tbody>';
-    $Ptr .= '<tr><td align="right"><b>Select Map</b></td>'."\n";
-    $Ptr .= '<td align="left">';
-    $Ptr .= &Apache::lonhtmlcommon::MapOptions(\%cache, 'ProblemStatistics',
-                                               'Statistics');
-    $Ptr .= '</td></tr>'."\n";
-    $Ptr .= '<tr><td align="right"><b>Sorting Type:</b></td>'."\n";
-    $Ptr .= '<td align="left">'."\n";
-    $Ptr .= &Apache::lonhtmlcommon::AscendOrderOptions(
-                                            $cache{'ProblemStatisticsAscend'}, 
-                                            'ProblemStatistics',
-                                            'Statistics');
-    $Ptr .= '</td></tr>'."\n";
-    $Ptr .= &ProblemStatisticsButtons($cache{'DisplayFormat'});
-    $Ptr .= '</table>';
-    $Ptr .= &ProblemStatisticsLegend();
-    $r->print($Ptr);
-
-    untie(%cache);
-    foreach (@$students) {
-        my $courseData = 
-            &Apache::loncoursedata::DownloadCourseInformation($_, $courseID);
-        last if ($c->aborted());
-        if(tie(%cache,'GDBM_File',$cacheDB,&GDBM_WRCREAT,0640)) {
-            &Apache::loncoursedata::ProcessStudentData(\%cache, 
-                                                       $courseData, $_);
-            untie(%cache);
-        }
-    }
-    if($c->aborted()) { return; }
-
-    unless(tie(%cache,'GDBM_File',$cacheDB,&GDBM_READER,0640)) {
-        return '<html><body>Unable to tie database.</body></html>';
-    }
-    my %discriminant=();
-    my @list=();
-    my %Discuss=&Apache::loncoursedata::LoadDiscussion($courseID);
-    my $index=0;
-    foreach (@$students) {
-	$index++;
-	#&Apache::lonstatistics::Update_PrgWin(++$index,$r);
-        &ExtractStudentData(\%cache, $_, \@list,\%Discuss, $r, \%discriminant);
+##
+## Localization notes:
+##
+## in @Fields[0]->{'long_title'} is placed in Excel files and is used as the
+## header for plots created with Graph.pm, both of which more than likely do
+## not support localization.
+##
+#
+#
+##
+## Description of Field attributes
+##
+## Attribute     Required   Value       Meaning or Use
+##
+## name            yes      any scalar  Used to uniquely identify field
+## title           yes      any scalar  This is what the user sees to identify
+##                                      the field.  Passed through &mt().
+## long_title      yes      any scalar  Used as graph heading and in excel
+##                                      output.  NOT translated
+## align           no    (left|right|center)  HTML cell contents alignment
+## color           yes      html color  HTML cell background color
+##                                      used to visually group statistics
+## special         no          (link)   Indicates a link, target is name.link
+##                                      Currently set in &get_statistics()
+## graphable       no      (yes|no)     Can a bar graph of the field be 
+##                                      produced?
+## sortable        no      (yes|no)     Should a sort link be put in the
+##                                      column header?
+## selectable      yes     (yes|no)     Can the column be removed from the
+##                                      statistics display?
+## selected        yes     (yes|no)     Is the column selected by default?
+##
+## format          no      sprintf format string
+##
+## excel_format    no      excel format type 
+##                               (see &Apache::loncommon::define_excel_formats
+my @Fields = (
+           { name => 'problem_num',
+             title => 'P#',
+             align => 'right',
+             color => '#FFFFE6',
+             selectable => 'no',
+             defaultselected => 'yes',
+           },
+           { name   => 'container',
+             title  => 'Sequence or Folder',
+             align  => 'left',
+             color  => '#FFFFE6',
+             sortable => 'yes',
+             selectable => 'no',
+             defaultselected => 'yes',
+           },
+           { name   => 'title',
+             title  => 'Title',
+             align  => 'left',
+             color  => '#FFFFE6',
+             special  => 'link',
+             sortable => 'yes', 
+             selectable => 'no',
+             defaultselected => 'yes',
+           },
+           { name   => 'part', 
+             title  => 'Part',
+             align  => 'left',
+             color  => '#FFFFE6',
+             selectable => 'no',
+             defaultselected => 'yes',
+           },
+           { name   => 'num_students',
+             title  => '#Stdnts',
+             align  => 'right',
+             color  => '#EEFFCC',
+             format => '%d',
+             sortable  => 'yes',
+             graphable => 'yes',
+             long_title => 'Number of Students Attempting Problem',
+             selectable => 'yes',
+             defaultselected => 'yes',
+           },
+           { name   => 'tries',
+             title  => 'Tries',
+             align  => 'right',
+             color  => '#EEFFCC',
+             format => '%d',
+             sortable  => 'yes',
+             graphable => 'yes',
+             long_title => 'Total Number of Tries',
+             selectable => 'yes',
+             defaultselected => 'yes',
+           },
+           { name   => 'max_tries',
+             title  => 'Max Tries',
+             align  => 'right',
+             color  => '#DDFFFF',
+             format => '%d',
+             sortable  => 'yes',
+             graphable => 'yes',
+             long_title => 'Maximum Number of Tries',
+             selectable => 'yes',
+             defaultselected => 'yes',
+           },
+           { name   => 'min_tries',
+             title  => 'Min Tries',
+             align  => 'right',
+             color  => '#DDFFFF',
+             format => '%d',
+             sortable  => 'yes',
+             graphable => 'yes',
+             long_title => 'Minumum Number of Tries',
+             selectable => 'yes',
+             defaultselected => 'yes',
+           },
+           { name   => 'mean_tries',
+             title  => 'Mean Tries',
+             align  => 'right',
+             color  => '#DDFFFF',
+             format => '%5.2f',
+             sortable  => 'yes',
+             graphable => 'yes',
+             long_title => 'Average Number of Tries',
+             selectable => 'yes',
+             defaultselected => 'yes',
+           },
+           { name   => 'std_tries',
+             title  => 'S.D. tries',
+             align  => 'right',
+             color  => '#DDFFFF',
+             format => '%5.2f',
+             sortable  => 'yes',
+             graphable => 'yes',
+             long_title => 'Standard Deviation of Number of Tries',
+             selectable => 'yes',
+             defaultselected => 'yes',
+           },
+           { name   => 'skew_tries',
+             title  => 'Skew Tries',
+             align  => 'right',
+             color  => '#DDFFFF',
+             format => '%5.2f',
+             sortable  => 'yes',
+             graphable => 'yes',
+             long_title => 'Skew of Number of Tries',
+             selectable => 'yes',
+             defaultselected => 'no',
+           },
+           { name   => 'num_solved',
+             title  => '#YES',
+             align  => 'right',
+             color  => '#FFDDDD',
+             format => '%4.1f',#             format => '%d',
+             sortable  => 'yes',
+             graphable => 'yes',
+             long_title => 'Number of Students able to Solve',
+             selectable => 'yes',
+             defaultselected => 'yes',
+           },
+           { name   => 'num_override',
+             title  => '#yes',
+             align  => 'right',
+             color  => '#FFDDDD',
+             format => '%4.1f',#             format => '%d',
+             sortable  => 'yes',
+             graphable => 'yes',
+             long_title => 'Number of Students given Override',
+             selectable => 'yes',
+             defaultselected => 'yes',
+           },
+           { name   => 'tries_per_correct',
+             title  => 'tries/correct',
+             align  => 'right',
+             color  => '#FFDDDD',
+             format => '%4.1f',
+             sortable  => 'yes',
+             graphable => 'yes',
+             long_title => 'Tries per Correct Answer',
+             selectable => 'yes',
+             defaultselected => 'yes',
+           },
+           { name   => 'num_wrong',
+             title  => '#Wrng',
+             align  => 'right',
+             color  => '#FFDDDD',
+             format => '%4.1f',
+             sortable  => 'yes',
+             graphable => 'yes',
+             long_title => 'Number of students whose final answer is wrong',
+             selectable => 'yes',
+             defaultselected => 'yes',
+           },
+           { name   => 'per_wrong',
+             title  => '%Wrng',
+             align  => 'right',
+             color  => '#FFDDDD',
+             format => '%4.1f',
+             sortable  => 'yes',
+             graphable => 'yes',
+             long_title => 'Percent of students whose final answer is wrong',
+             selectable => 'yes',
+             defaultselected => 'yes',
+           },
+           { name   => 'deg_of_diff',
+             title  => 'DoDiff',
+             align  => 'right',
+             color  => '#FFFFE6',
+             format => '%5.2f',
+             sortable  => 'yes',
+             graphable => 'yes',
+             long_title => 'Degree of Difficulty'.
+                           '[ 1 - ((#YES+#yes) / Tries) ]',
+             selectable => 'yes',
+             defaultselected => 'yes',
+           },
+           { name   => 'deg_of_disc',
+             title  => 'DoDisc',
+             align  => 'right',
+             color  => '#FFFFE6',
+             format => '%4.2f',
+             sortable  => 'yes',
+             graphable => 'yes',
+             long_title => 'Degree of Discrimination',
+             selectable => 'yes',
+             defaultselected => 'yes',
+           },
+##   duedate included for research purposes.  Commented out most of the time.
+#           { name => 'duedate',
+#             title => 'Due Date',
+#             align => 'left',
+#             color => '#FFFFFF',
+#             sortable => 'yes',
+#             graphable => 'no',
+#             long_title => 'Due date of resource for instructor',
+#             selectable => 'no',
+#             defaultselected => 'yes',
+#            },
+##   opendate included for research purposes.  Commented out most of the time.
+#           { name => 'opendate',
+#             title => 'Open Date',
+#             align => 'left',
+#             color => '#FFFFFF',
+#             sortable => 'yes',
+#             graphable => 'no',
+#             long_title => 'date resource became answerable',
+#             selectable => 'no',
+#             defaultselected => 'yes',
+#            },
+##   symb included for research purposes.  Commented out most of the time.
+#           { name => 'symb',
+#             title => 'Symb',
+#             align => 'left',
+#             color => '#FFFFFF',
+#             sortable => 'yes',
+#             graphable => 'no',
+#             long_title => 'Unique LON-CAPA identifier for problem',
+#             selectable => 'no',
+#             defaultselected => 'yes',
+#            },
+##   resptypes included for research purposes.  Commented out most of the time.
+#           { name => 'resptypes',
+#             title => 'Response Types',
+#             align => 'left',
+#             color => '#FFFFFF',
+#             sortable => 'no',
+#             graphable => 'no',
+#             long_title => 'Response Types used in this problem',
+#             selectable => 'no',
+#             defaultselected => 'yes',
+#            },
+##   maxtries included for research purposes.  Commented out most of the time.
+#           { name => 'maxtries',
+#             title => 'Maxtries',
+#             align => 'left',
+#             color => '#FFFFFF',
+#             sortable => 'no',
+#             graphable => 'no',
+#             long_title => 'Maximum number of tries',
+#             selectable => 'no',
+#             defaultselected => 'yes',
+#            },
+##   hinttries included for research purposes.  Commented out most of the time.
+#           { name => 'hinttries',
+#             title => 'hinttries',
+#             align => 'left',
+#             color => '#FFFFFF',
+#             sortable => 'no',
+#             graphable => 'no',
+#             long_title => 'Number of tries before a hint appears',
+#             selectable => 'no',
+#             defaultselected => 'yes',
+#            },
+#
+##   problem weight for instructor
+           { name => 'weight',
+             title => 'weight',
+             align => 'right',
+             color => '#FFFFFF',
+             sortable => 'no',
+             graphable => 'no',
+             long_title => 'Problem weight (for instructor)',
+             selectable => 'yes',
+             defaultselected => 'yes',
+            },
+);
+
+my @SeqFields = (
+           { name   => 'title',
+             title  => 'Sequence',
+             align  => 'left',
+             color  => '#FFFFE6',
+             special  => 'no',
+             sortable => 'no', 
+             selectable => 'yes',
+             defaultselected => 'no',
+           },
+           { name   => 'items',
+             title  => '#Items',
+             align  => 'right',
+             color  => '#FFFFE6',
+             format => '%4d',
+             sortable  => 'no',
+             graphable => 'no',
+             long_title => 'Number of Items in Sequence',
+             selectable => 'yes',
+             defaultselected => 'no',
+           },
+           { name   => 'scoremean',
+             title  => 'Score Mean',
+             align  => 'right',
+             color  => '#FFFFE6',
+             format => '%4.2f',
+             sortable  => 'no',
+             graphable => 'no',
+             long_title => 'Mean Sequence Score',
+             selectable => 'yes',
+             defaultselected => 'no',
+           },
+           { name   => 'scorestd',
+             title  => 'Score STD',
+             align  => 'right',
+             color  => '#FFFFE6',
+             format => '%4.2f',
+             sortable  => 'no',
+             graphable => 'no',
+             long_title => 'Standard Deviation of Sequence Scores',
+             selectable => 'yes',
+             defaultselected => 'no',
+           },
+           { name   => 'scoremax',
+             title  => 'Score Max',
+             align  => 'right',
+             color  => '#FFFFE6',
+             format => '%4.2f',
+             sortable  => 'no',
+             graphable => 'no',
+             long_title => 'Maximum Sequence Score',
+             selectable => 'yes',
+             defaultselected => 'no',
+           },
+           { name   => 'scoremin',
+             title  => 'Score Min',
+             align  => 'right',
+             color  => '#FFFFE6',
+             format => '%4.2f',
+             sortable  => 'no',
+             graphable => 'no',
+             long_title => 'Minumum Sequence Score',
+             selectable => 'yes',
+             defaultselected => 'no',
+           },
+           { name   => 'scorecount',
+             title  => 'Score N',
+             align  => 'right',
+             color  => '#FFFFE6',
+             format => '%4d',
+             sortable  => 'no',
+             graphable => 'no',
+             long_title => 'Number of Students in score computations',
+             selectable => 'yes',
+             defaultselected => 'no',
+           },
+           { name   => 'countmean',
+             title  => 'Count Mean',
+             align  => 'right',
+             color  => '#FFFFFF',
+             format => '%4.2f',
+             sortable  => 'no',
+             graphable => 'no',
+             long_title => 'Mean Sequence Score',
+             selectable => 'yes',
+             defaultselected => 'no',
+           },
+           { name   => 'countstd',
+             title  => 'Count STD',
+             align  => 'right',
+             color  => '#FFFFFF',
+             format => '%4.2f',
+             sortable  => 'no',
+             graphable => 'no',
+             long_title => 'Standard Deviation of Sequence Scores',
+             selectable => 'yes',
+             defaultselected => 'no',
+           },
+           { name   => 'countmax',
+             title  => 'Count Max',
+             align  => 'right',
+             color  => '#FFFFFF',
+             format => '%4.2f',
+             sortable  => 'no',
+             graphable => 'no',
+             long_title => 'Maximum Number of Correct Problems',
+             selectable => 'yes',
+             defaultselected => 'no',
+           },
+           { name   => 'countmin',
+             title  => 'Count Min',
+             align  => 'right',
+             color  => '#FFFFFF',
+             format => '%4.2f',
+             sortable  => 'no',
+             graphable => 'no',
+             long_title => 'Minumum Number of Correct Problems',
+             selectable => 'yes',
+             defaultselected => 'no',
+           },
+           { name   => 'count',
+             title  => 'Count N',
+             align  => 'right',
+             color  => '#FFFFFF',
+             format => '%4d',
+             sortable  => 'no',
+             graphable => 'no',
+             long_title => 'Number of Students in score computations',
+             selectable => 'yes',
+             defaultselected => 'no',
+           },
+           { name   => 'KR-21',
+             title  => 'KR-21',
+             align  => 'right',
+             color  => '#FFAAAA',
+             format => '%4.2f',
+             sortable  => 'no',
+             graphable => 'no',
+             long_title => 'KR-21 reliability statistic',
+             selectable => 'yes',
+             defaultselected => 'no',
+           },           
+);
+
+my %SelectedFields;
+
+sub parse_field_selection {
+    #
+    # Pull out the defaults
+    if (! defined($env{'form.fieldselections'})) {
+        $env{'form.fieldselections'} = [];
+        foreach my $field (@Fields) {
+            next if ($field->{'selectable'} ne 'yes');
+            if ($field->{'defaultselected'} eq 'yes') {
+                push(@{$env{'form.fieldselections'}},$field->{'name'});
+            }
+        }
     }
-    #&Apache::lonstatistics::Close_PrgWin($r);
- 
-    my ($upper, $lower) = &Discriminant(\%discriminant,$r);
-    my %Header = (0,"Homework Sets Order",1,"#Stdnts",2,"Tries",3,"Mod",
-                  4,"Mean",5,"#YES",6,"#yes",7,"%Wrng",8,"DoDiff",
-                  9,"S.D.",10,"Skew.",11,"D.F.1st",12,"D.F.2nd", 13, "Disc.");
-    my $color=&setbgcolor(0);
-    my %GraphDat= &BuildStatisticsTable(\%cache, $upper, $lower, \@list, 
-                                        \%Header, $students, $r, $color);
-    untie(%cache);
+    #
+    # Make sure the data we are plotting is there
+    my %NeededFields;
+    if (exists($env{'form.plot'}) && $env{'form.plot'} ne '' &&
+        $env{'form.plot'} ne 'none') {
+        if ($env{'form.plot'} eq 'degrees') {
+            $NeededFields{'deg_of_diff'}++;
+            $NeededFields{'deg_of_disc'}++;
+        } elsif ($env{'form.plot'} eq 'tries statistics') {
+            $NeededFields{'mean_tries'}++;
+            $NeededFields{'std_tries'}++;
+            $NeededFields{'problem_num'}++;
+        } else {
+            $NeededFields{$env{'form.plot'}}++;
+        }
+    }
+    #
+    # This should not happen, but in case it does...
+    if (ref($env{'form.fieldselections'}) ne 'ARRAY') {
+        $env{'form.fieldselections'} = [$env{'form.fieldselections'}];
+    }
+    #
+    # Set the field data and the selected fields (for easier checking)
+    undef(%SelectedFields);
+    foreach my $field (@Fields) {
+        if ($field->{'selectable'} ne 'yes') {
+            $field->{'selected'} = 'yes';
+        } else {
+            $field->{'selected'} = 'no';
+        }
+        if (exists($NeededFields{$field->{'name'}})) {
+            $field->{'selected'} = 'yes';
+            $SelectedFields{$field->{'name'}}++;
+        }
+        foreach my $selection (@{$env{'form.fieldselections'}}) {
+            if ($selection eq $field->{'name'} || $selection eq 'all') {
+                $field->{'selected'} = 'yes';
+                $SelectedFields{$field->{'name'}}++;
+            }
+        }
+    }
+    #
+    # Always show all the sequence statistics (for now)
+    foreach my $field (@SeqFields) {
+        $field->{'selected'} = 'yes';
+    }
+    return;
 }
 
+sub field_selection_input {
+    my $Str = '<select name="fieldselections" multiple size="5">'."\n";
+    $Str .= '<option value="all">all</option>'."\n";
+    foreach my $field (@Fields) {
+        next if ($field->{'selectable'} ne 'yes');
+        $Str .= '    <option value="'.$field->{'name'}.'" ';
+        if ($field->{'selected'} eq 'yes') {
+            $Str .= 'selected ';
+        }
+        $Str .= '>'.$field->{'title'}.'</option>'."\n";
+    }
+    $Str .= "</select>\n";
+}
 
-#---- Problem Statistics Web Page ---------------------------------------
+###############################################
+###############################################
 
+=pod 
 
-sub NumericSort {          
-    $a <=> $b;
+=item &CreateInterface()
+
+Create the main intereface for the statistics page.  Allows the user to
+select sections, maps, and output.
+
+=cut
+
+###############################################
+###############################################
+sub CreateInterface {
+    my ($r) = @_;
+    #
+    &parse_field_selection();
+    #
+    my $Str = '';
+    $Str .= &Apache::lonhtmlcommon::breadcrumbs('Overall Problem Statistics',
+						'Statistics_Overall_Key');
+    $Str .= '<table cellspacing="5">'."\n";
+    $Str .= '<tr>';
+    $Str .= '<td align="center"><b>'.&mt('Sections').'</b></td>';
+    $Str .= '<td align="center"><b>'.&mt('Groups').'</b></td>';
+    $Str .= '<td align="center"><b>'.&mt('Access Status').'</b></td>';
+    $Str .= '<td align="center"><b>'.&mt('Sequences and Folders').'</b></td>';
+    $Str .= '<td align="center"><b>'.&mt('Statistics').'</b></td>';
+    $Str .= '<td rowspan="2">'.
+        &Apache::lonstathelpers::limit_by_time_form().'</td>';
+    $Str .= '</tr>'."\n";
+    #
+    $Str .= '<tr><td align="center">'."\n";
+    $Str .= &Apache::lonstatistics::SectionSelect('Section','multiple',5);
+    $Str .= '</td><td align="center">';
+    $Str .= &Apache::lonstatistics::GroupSelect('Group','multiple',5);
+    $Str .= '</td><td align="center">';
+    $Str .= &Apache::lonhtmlcommon::StatusOptions(undef,undef,5);
+    $Str .= '</td><td align="center">';
+    #
+    $Str .= &Apache::lonstatistics::map_select('Maps','multiple,all',5);
+    $Str .= '</td><td>'.&field_selection_input();
+    $Str .= '</td></tr>'."\n";
+    $Str .= '</table>'."\n";
+    #
+    $Str .= '<p>'.&mt('Status: [_1]',
+                         '<input type="text" '.
+                         'name="stats_status" size="60" value="" />'
+                         ).
+                         '</nobr></p>';
+    #
+    $Str .= '<input type="submit" name="GenerateStatistics" value="'.
+        &mt('Generate Statistics').'" />';
+    $Str .= '&nbsp;'x5;
+    $Str .= 'Plot '.&plot_dropdown().('&nbsp;'x10);
+    #
+    return $Str;
 }
 
+###############################################
+###############################################
 
-sub CreateProblemStatisticsTableHeading {
-    my ($displayFormat,$sequenceSource,$sequenceTitle,$headings,$r)=@_;
-    if($displayFormat eq 'Display CSV Format') {
-        $r->print('<br>"'.$sequenceTitle.'","');
-        $r->print($sequenceSource.'"');
-	return;
-    }
+=pod 
+
+=item &BuildProblemStatisticsPage()
+
+Main interface to problem statistics.
+
+=cut
 
-    $r->print('<br><a href="'.$sequenceSource.
-              '" target="_blank">'.$sequenceTitle.'</a>');
+###############################################
+###############################################
+my $navmap;
+my @sequences;
+
+sub clean_up {
+    undef($navmap);
+    undef(@sequences);
+}
 
-    my $Result = "\n".'<table border=2><tr><th>P#</th>'."\n";
-    for(my $nIndex=0; $nIndex < (scalar (keys %$headings)); $nIndex++) { 
-	$Result .= '<th>'.'<input type="submit" name="';
-        $Result .= 'ProblemStatisticsHeading" value="';
-        $Result .= $headings->{$nIndex}.'" />'.'</th>'."\n";
+sub BuildProblemStatisticsPage {
+    my ($r,$c)=@_;
+    undef($navmap);
+    undef(@sequences);
+    #
+    my %Saveable_Parameters = ('Status' => 'scalar',
+                               'statsoutputmode' => 'scalar',
+                               'Section' => 'array',
+                               'Groups' => 'array',
+                               'StudentData' => 'array',
+                               'Maps' => 'array',
+                               'fieldselections'=> 'array');
+    &Apache::loncommon::store_course_settings('statistics',
+                                              \%Saveable_Parameters);
+    &Apache::loncommon::restore_course_settings('statistics',
+                                                \%Saveable_Parameters);
+    #
+    &Apache::lonstatistics::PrepareClasslist();
+    #
+    # Clear the package variables
+    undef(@StatsArray);
+    undef(%SeqStat);
+    #
+    # Finally let the user know we are here
+    my $interface = &CreateInterface($r);
+    $r->print($interface);
+    $r->print('<input type="hidden" name="sortby" value="'.$env{'form.sortby'}.
+              '" />');
+    #
+    my @CacheButtonHTML = 
+        &Apache::lonstathelpers::manage_caches($r,'Statistics','stats_status');
+    my $Str;
+    foreach my $html (@CacheButtonHTML) {
+        $Str.=$html.('&nbsp;'x5);
+    }
+    #
+    $r->print($Str);
+    if (! exists($env{'form.firstrun'})) {
+        $r->print('<h3>'.
+                  &mt('Press "Generate Statistics" when you are ready.').
+                  '</h3><p>'.
+                  &mt('It may take some time to update the student data '.
+                      'for the first analysis.  Future analysis this session '.
+                      ' will not have this delay.').
+                  '</p>');
+	&clean_up();
+        return;
     }
-    $Result .= "\n".'</tr>'."\n";    
-    $r->print($Result);
     $r->rflush();
+    #
+    # This probably does not need to be done each time we are called, but
+    # it does not slow things down noticably.
+    &Apache::loncoursedata::populate_weight_table();
+    #
+    ($navmap,@sequences) = 
+        &Apache::lonstatistics::selected_sequences_with_assessments();
+    if (! ref($navmap)) {
+        $r->print('<h1>'.&mt('A course-wide error occured.').'</h1>'.
+                  '<h3>'.$navmap.'</h3>');
+	&clean_up();
+        return;
+    }
+    if (exists($env{'form.Excel'})) {
+        $r->print('<h4>'.
+                  &Apache::lonstatistics::section_and_enrollment_description().
+                  '</h4>');
+        &Excel_output($r);
+    } else { 
+        $r->print('<input type="submit" name="Excel" value="'.
+                  &mt('Produce Excel Output').'" />'.'&nbsp;'x5);
+        $r->rflush();
+        $r->print('<h4>'.
+                  &Apache::lonstatistics::section_and_enrollment_description().
+                  '</h4>');
+        my $count = 0;
+        foreach my $seq (@sequences) {
+            my @resources = 
+                &Apache::lonstathelpers::get_resources($navmap,$seq);
+            $count += scalar(@resources);
+        }
+        if ($count > 10) {
+            $r->print('<h2>'.
+                      &mt('Compiling statistics for [_1] problems',$count).
+                      '</h2>');
+            if ($count > 30) {
+                $r->print('<h3>'.&mt('This will take some time.').'</h3>');
+            }
+            $r->rflush();
+        }
+        #
+        my $sortby = $env{'form.sortby'};
+        $sortby = 'container' if (! defined($sortby) || $sortby =~ /^\s*$/);
+        my $plot = $env{'form.plot'};
+        if ($plot eq '' || $plot eq 'none') {
+            undef($plot);
+        }
+        if ($sortby eq 'container' && ! defined($plot)) {
+            &output_sequence_statistics($r);
+            &output_html_by_sequence($r);
+        } else {
+            if (defined($plot)) {
+                &make_plot($r,$plot);
+            }
+            &output_html_stats($r);
+            &output_sequence_statistics($r);
+        }
+    }
+    &clean_up();
+    return;
 }
 
-sub CloseTable {
-    my ($cache,$r)=@_;
-    if($cache->{'DisplayFormat'} eq 'Display CSV Format') {
-	return;
-    }    
-    $r->print("\n".'</table>'."\n");
+sub output_sequence_statistics {
+    my ($r) = @_;
+    my $c=$r->connection();
+    $r->print('<h2>'.&mt('Sequence Statistics').
+	      &Apache::loncommon::help_open_topic('Statistics_Sequence').
+	      '</h2>');
+    $r->print('<table border="0"><tr><td bgcolor="#777777">'."\n".
+              '<table border="0" cellpadding="3">'."\n".
+              '<tr bgcolor="#FFFFE6">');
+    $r->print(&sequence_html_header());
+    foreach my $seq (@sequences) { 
+        last if ($c->aborted);
+        &compute_sequence_statistics($seq);
+        $r->print(&sequence_html_output($seq));
+    }
+    $r->print('</table>');
+    $r->print('</table>');
     $r->rflush();
+    return;
 }
 
 
- 
-# ------ Dump the Student's DB file and handling the data for statistics table 
-sub ExtractStudentData {
-    my ($cache,$name,$list,$Discuss,$r,$discriminant)=@_;
-    my $totalTries = 0;
-    my $totalAwarded = 0;
-    my $spent=0;
-    my $spent_yes=0;
-    my $TotDiscuss=0;
-    my $TotalOpend = 0;
-    my $ProbSolved = 0;
-    my $ProbTot = 0;
-    my $TotFirst = 0;
-    my $TimeTot = 0;
-    my $Discussed=0;
-    my $discrim='';
-    my $tempSequenceOrder=100;
-
-#$Apache::lonxml::debug=1;
-#&Apache::lonhomework::showhash(%$cache);
-#$Apache::lonxml::debug=0;
-
-    foreach my $sequence (split(':', $cache->{'orderedSequences'})) {
-	my $tempProblemOrder=100;
-        if($cache->{'ProblemStatisticsMaps'} ne 'All Maps'  &&
-           $cache->{'ProblemStatisticsMaps'} ne $cache->{$sequence.':title'}) {
-#	    $r->print("<br>sequences=$cache->{'orderedSequences'}");
-#	    $r->print("<br>".$cache->{$sequence.':title'});
-            next;
+##########################################################
+##########################################################
+##
+## HTML output routines
+##
+##########################################################
+##########################################################
+sub output_html_by_sequence {
+    my ($r) = @_;
+    my $c = $r->connection();
+    $r->print(&html_preamble());
+    #
+    foreach my $seq (@sequences) {
+        last if ($c->aborted);
+        $r->print("<h3>".$seq->compTitle."</h3>".
+                  '<table border="0"><tr><td bgcolor="#777777">'."\n".
+                  '<table border="0" cellpadding="3">'."\n".
+                  '<tr bgcolor="#FFFFE6">'.
+                  &statistics_table_header('no container')."</tr>\n");
+        my @Data = &compute_statistics_on_sequence($seq);
+        foreach my $data (@Data) {
+            $r->print('<tr>'.&statistics_html_table_data($data,
+                                                         'no container').
+                      "</tr>\n");
         }
-	$tempSequenceOrder++;
+        $r->print('</table>'."\n".'</table>'."\n");
+        $r->rflush();
+    }
+    return;
+}
 
-        #$discrim .= '&';
-        foreach my $problemID (split(':', $cache->{$sequence.':problems'})) {
-#	    $r->print("<br>problems=$cache->{$sequence.':problems'}");
-            my $problem = $cache->{$problemID.':problem'};
-#	    $r->print("<br>$problemID === $problem");
-            my $LatestVersion = $cache->{$name.':version:'.$problem};
-	    # Output dashes for all the parts of this problem if there
-            # is no version information about the current problem.
-            #if(!$LatestVersion) {
-            #    foreach my $part (split(/\:/,$cache->{$sequence.':'.
-            #                                          $problemID.
-            #                                          ':parts'})) {
-            #        $codes    .= "-,";
-            #        $attempts .= "0,"; 
-            #    }
-            #    next;
-            #}
-
-            my %partData=undef;
-	    $partData{'count'}=0;
-            # Initialize part data, display skips correctly
-            # Skip refers to when a student made no submissions on that
-            # part/problem.
-            foreach my $part (split(/\:/,$cache->{$sequence.':'.
-                                                  $problemID.
-                                                  ':parts'})) {
-		$tempProblemOrder++;
-		$partData{'count'}++;
-#		$r->print("<br>parts=$cache->{$sequence.':'.$problemID.':parts'}");
-                $partData{$part.':order'}=$tempProblemOrder;
-                $partData{$part.':tries'}=0;
-                $partData{$part.':code'}='-';
-            }
+sub output_html_stats {
+    my ($r)=@_;
+    &compute_all_statistics($r);
+    $r->print(&html_preamble());
+    &sort_data($env{'form.sortby'});
+    #
+    my $count=0;
+    foreach my $data (@StatsArray) {
+        if ($count++ % 50 == 0) {
+            $r->print("</table>\n</table>\n");
+            $r->print('<table border="0"><tr><td bgcolor="#777777">'."\n".
+                      '<table border="0" cellpadding="3">'."\n".
+                      '<tr bgcolor="#FFFFE6">'.
+                      '<tr bgcolor="#FFFFE6">'.
+                      &statistics_table_header().
+                      "</tr>\n");
+        }
+        $r->print('<tr>'.&statistics_html_table_data($data)."</tr>\n");
+    }
+    $r->print("</table>\n</table>\n");
+    return;
+}
 
-            # Looping through all the versions of each part, starting with the
-            # oldest version.  Basically, it gets the most recent 
-            # set of grade data for each part.
-	    for(my $Version=1; $Version<=$LatestVersion; $Version++) {
-		foreach my $part (split(/\:/,$cache->{$sequence.':'.
-                                                      $problemID.
-                                                      ':parts'})) {
-
-                    if(!defined($cache->{$name.":$Version:$problem".
-                                               ":resource.$part.solved"})) {
-                        # No grade for this submission, so skip
-                        next;
-                    }
+sub html_preamble {
+    my $Str='';
+    $Str .= "<h2>".
+        $env{'course.'.$env{'request.course.id'}.'.description'}.
+        "</h2>\n";
+    my ($starttime,$endtime) = &Apache::lonstathelpers::get_time_limits();
+    if (defined($starttime) || defined($endtime)) {
+        # Inform the user what the time limits on the data are.
+        $Str .= '<h3>'.&mt('Statistics on submissions from [_1] to [_2]',
+                           &Apache::lonlocal::locallocaltime($starttime),
+                           &Apache::lonlocal::locallocaltime($endtime)
+                           ).'</h3>';
+    }
+    $Str .= "<h3>".&mt('Compiled on [_1]',
+                       &Apache::lonlocal::locallocaltime(time))."</h3>";
+    return $Str;
+}
 
-                    my $tries=0;
-                    my $time=0;
-                    my $awarded=0;
-		    $Discussed=0;
-                    my $code='-';
-
-                    $awarded = $cache->{"$name:$Version:$problem:resource.".
-                                        "$part.awarded"};
-                    $partData{$part.':awarded'} = ($awarded) ? $awarded : 0;
-                    $totalAwarded += $awarded;
-
-                    $tries = $cache->{"$name:$Version:$problem".
-                                      ":resource.$part.tries"};
-                    $partData{$part.':tries'} = ($tries) ? $tries : 0;
-                    $partData{$part.':wrong'} = $partData{$part.':tries'};
-                    $totalTries += $tries;
-
-                    my $val = $cache->{$name.":$Version:$problem".
-                                       ":resource.$part.solved"};
-                    if    ($val eq 'correct_by_student')   {$code = 'C';} 
-                    elsif ($val eq 'correct_by_override')  {$code = 'O';}
-                    elsif ($val eq 'incorrect_attempted')  {$code = 'I';} 
-                    elsif ($val eq 'incorrect_by_override'){$code = 'I';}
-                    elsif ($val eq 'excused')              {$code = 'x';}
-                    $partData{$part.':code'}=$code;
-                    if($partData{$part.':wrong'} ne 0 && 
-                       ($code eq 'C' || $code eq 'O')) {
-                        $partData{$part.':wrong'}--;
-                    }
-                }
+
+###############################################
+###############################################
+##
+## Misc HTML output routines
+##
+###############################################
+###############################################
+sub statistics_html_table_data {
+    my ($data,$options) = @_;
+    my $row = '';
+    foreach my $field (@Fields) {
+        next if ($options =~ /no $field->{'name'}/);
+        next if ($field->{'selected'} ne 'yes');
+        $row .= '<td bgcolor="'.$field->{'color'}.'"';
+        if (exists($field->{'align'})) {
+            $row .= ' align="'.$field->{'align'}.'"';
             }
+        $row .= '>';
+        if (exists($field->{'special'}) && $field->{'special'} eq 'link') {
+            $row .= '<a href="'.$data->{$field->{'name'}.'.link'}.'">';
+        }
+        if (exists($field->{'format'}) && $data->{$field->{'name'}} !~ /[A-Z]/i) {
+            $row .= sprintf($field->{'format'},$data->{$field->{'name'}});
+        } else {
+            $row .= $data->{$field->{'name'}};
+        }
+        if (exists($field->{'special'}) && $field->{'special'} eq 'link') {
+            $row.= '</a>';
+        }
+        $row .= '</td>';
+    }
+    return $row;
+}
 
-#$Apache::lonxml::debug=1;
-#&Apache::lonhomework::showhash(%partData);
-#$Apache::lonxml::debug=0;
-
-            # Loop through all the parts for the current problem in the 
-            # correct order and prepare the output
-	    my $partCounter=0;
-            foreach (split(/\:/,$cache->{$sequence.':'.$problemID.
-                                         ':parts'})) {
-		$partCounter++;
-                my $Yes = 0;
-                if($partData{$_.':code'} eq 'C' || 
-                   $partData{$_.':code'} eq 'O') {
-                    $Yes=1;
-                }
-                my $pOrder=$partData{$_.':order'};
-                my $ptr = $tempSequenceOrder.':'.$pOrder.':'.$problemID;
+sub statistics_table_header {
+    my ($options) = @_;
+    my $header_row;
+    foreach my $field (@Fields) {
+        next if ($options =~ /no $field->{'name'}/);
+        next if ($field->{'selected'} ne 'yes');
+        $header_row .= '<th>';
+        if (exists($field->{'sortable'}) && $field->{'sortable'} eq 'yes') {
+            $header_row .= '<a href="javascript:'.
+                'document.Statistics.sortby.value='."'".$field->{'name'}."'".
+                    ';document.Statistics.submit();">';
+        }
+        $header_row .= &mt($field->{'title'});
+        if ($options =~ /sortable/) {
+            $header_row.= '</a>';
+        }
+        if ($options !~ /no plots/        && 
+            exists($field->{'graphable'}) && 
+            $field->{'graphable'} eq 'yes') {
+            $header_row.=' (';
+            $header_row .= '<a href="javascript:'.
+                "document.Statistics.plot.value='$field->{'name'}'".
+                    ';document.Statistics.submit();">';
+            $header_row .= &mt('plot').'</a>)';
+        }
+        $header_row .= '</th>';
+    }
+    return $header_row;
+}
 
-                if($partData{'count'} > 1) {
-                    $ptr .= "*(part $_)";
-                }
-                #if($partCounter > 1) {
-                    $discrim .= '&';
-                #}
-
-		my ($pr_no,$dod)=split('&',$ptr);
-#		my $DoDiff=$DoDiff->{$dod};
-#               $r->print('<br>'.$name.'---'.$ptr.'==='.$DoDiff);
-
-                my $Fac = ($partData{$_.':tries'}) ? 
-                    ($partData{$_.':awarded'}/$partData{$_.':tries'}) : 0;
-                my $DisF;
-                if($Fac > 0 &&  $Fac < 1) { 
-                    $DisF = sprintf( "%.4f", $Fac );
-                } else {
-                    $DisF = $Fac;
-                }
+sub sequence_html_header {
+    my $Str .= '<tr>';
+    foreach my $field (@SeqFields) {
+#        next if ($field->{'selected'} ne 'yes');
+        $Str .= '<th bgcolor="'.$field->{'color'}.'"';
+        $Str .= '>'.$field->{'title'}.'</th>';
+    }
+    $Str .= '</tr>';
+    return $Str;
+}
 
-                if ($Discuss->{"$name:$problem"}) {
-		    $TotDiscuss++;
-                    $Discussed=1;
-                }
-                my $time = $cache->{"$name:$LatestVersion:$problem:timestamp"};
-                $discrim .= $tempSequenceOrder.'@'.$pOrder.'='.$DisF.'+'.$Yes;
-                $ptr .= '&'.$partData{$_.':tries'}.
-                        '&'.$partData{$_.':wrong'}.
-                        '&'.$partData{$_.':code'};
-                push (@$list, $ptr."&$Discussed");
-#                $r->print('<br>'.$_.$name.'---'.$ptr);
-		
-####		if ($DoDiff>0.85) {
 
-                $TimeTot += $time;
+sub sequence_html_output {
+    my ($seq) = @_;
+    my $data = $SeqStat{$seq->symb};
+    my $row = '<tr>';
+    foreach my $field (@SeqFields) {
+        next if ($field->{'selected'} ne 'yes');
+        $row .= '<td bgcolor="'.$field->{'color'}.'"';
+        if (exists($field->{'align'})) {
+            $row .= ' align="'.$field->{'align'}.'"';
+        }
+        $row .= '>';
+        if (exists($field->{'format'})) {
+            $row .= sprintf($field->{'format'},$data->{$field->{'name'}});
+        } else {
+            $row .= $data->{$field->{'name'}};
+        }
+        $row .= '</td>';
+    }
+    $row .= '</tr>'."\n";
+    return $row;
+}
 
-                if ($Yes==1 && $partData{$_.':tries'}==1) {
-		    $TotFirst++;
-                }
-#		my $Acts= $Activity->{$name.':'.$problem};
-#		if ($Acts) {
-#		    my $Pt=&ProcAct( $Acts, $time );
-		    #my ($spe,$beg) = split(/\+/,$Pt);
-#                    my $spe= $Pt;
-#		    if ($Yes==1) {$spent_yes += $spe;}
-#		    $spent += $spe;
-		    #$Beg += $beg;
-#                   $r->print('<br>'.$name.'---'.$problem.'---'.$spe);
-#		}
-		$TotalOpend++;
-		$ProbTot++;
+####################################################
+####################################################
+##
+##    Plotting Routines
+##
+####################################################
+####################################################
+sub make_plot {
+    my ($r,$plot) = @_;
+    &compute_all_statistics($r);
+    &sort_data($env{'form.sortby'});
+    if ($plot eq 'degrees') {
+        &degrees_plot($r);
+    } elsif ($plot eq 'tries statistics') {
+        &tries_data_plot($r);
+    } else {
+        &make_single_stat_plot($r,$plot);
+    }
+    return;
+}
 
-                $tempProblemOrder++;
-            }
+sub make_single_stat_plot {
+    my ($r,$datafield) = @_;
+    #
+    my $title; my $yaxis;
+    foreach my $field (@Fields) {
+        next if ($field->{'name'} ne $datafield);
+        $title = $field->{'long_title'};
+        $yaxis = $field->{'title'};
+        last;
+    }
+    if ($title eq '' || $yaxis eq '') {
+        # datafield is something we do not know enough about to plot
+        $r->print('<h3>'.
+                  &mt('Unable to plot the requested statistic.').
+                  '</h3>');
+        return;
+    }
+    #
+    # Build up the data sets to plot
+    my @Labels; 
+    my @Data;
+    my $max = 1;
+    foreach my $data (@StatsArray) {
+        push(@Labels,$data->{'problem_num'});
+        push(@Data,$data->{$datafield});
+        if ($data->{$datafield}>$max) {
+            $max = $data->{$datafield};
         }
     }
-    my $pstr;
-    if($totalTries) {
-	my $DisFac = ($totalAwarded/$totalTries);
-	my $DisFactor = sprintf( "%.4f", $DisFac );
-        my $TS = sprintf( "%.2f", $spent );
-        my $TS_yes = sprintf( "%.2f", $spent_yes );
-	$pstr=$DisFactor.':'.$name.':'.$ProbTot.':'.$TotalOpend.':'.
-              $totalTries.':'.$ProbSolved.':'.$TotFirst.':'.
-              $TS_yes.':'.$TS.':'.$TotDiscuss;
-	(%$discriminant)->{$pstr}=$discrim;
+    foreach (1,2,3,4,5,10,15,20,25,40,50,75,100,150,200,250,300,500,600,750,
+             1000,1500,2000,2500,3000,3500,4000,5000,7500,10000,15000,20000) {
+        if ($max <= $_) {
+            $max = $_;
+            last;
+        }
+    }
+    if ($max > 20000) {
+        $max = 10000*(int($max/10000)+1);
     }
+    #
+    $r->print("<p>".&Apache::loncommon::DrawBarGraph($title,
+                                                     'Problem Number',
+                                                     $yaxis,
+                                                     $max,
+                                                     undef, # colors
+                                                     \@Labels,
+                                                     \@Data)."</p>\n");
+    return;
 }
 
-
-=pod
-sub MySort {          
-    if ( $Pos > 0 ) {
-	if ($ENV{'form.order'} eq 'Descending') {$b <=> $a;}
-	else { $a <=> $b; }
-    }
-    else {
-	if ($ENV{'form.order'} eq 'Descending') {$b cmp $a;}
-	else { $a cmp $b; }
+sub degrees_plot {
+    my ($r)=@_;
+    my $count = scalar(@StatsArray);
+    my $width = 50 + 10*$count;
+    $width = 300 if ($width < 300);
+    my $height = 300;
+    my $plot = '';
+    my $ymax = 0;
+    my $ymin = 0;
+    my @Disc; my @Diff; my @Labels;    
+    foreach my $data (@StatsArray) {
+        push(@Labels,$data->{'problem_num'});
+        my $disc = $data->{'deg_of_disc'};
+        my $diff = $data->{'deg_of_diff'};
+        push(@Disc,$disc);
+        push(@Diff,$diff);
+        #
+        $ymin = $disc if ($ymin > $disc);
+        $ymin = $diff if ($ymin > $diff);
+        $ymax = $disc if ($ymax < $disc);
+        $ymax = $diff if ($ymax < $diff);
     }
+    #
+    # Make sure we show relevant information.
+    if ($ymin < 0) {
+        if (abs($ymin) < 0.05) {
+            $ymin = 0;
+        } else {
+            $ymin = -1;
+        }
+    }
+    if ($ymax > 0) {
+        if (abs($ymax) < 0.05) {
+            $ymax = 0;
+        } else {
+            $ymax = 1;
+        }
+    }
+    #
+    my $xmax = $Labels[-1];
+    if ($xmax > 50) {
+        if ($xmax % 10 != 0) {
+            $xmax = 10 * (int($xmax/10)+1);
+        }
+    } else {
+        if ($xmax % 5 != 0) {
+            $xmax = 5 * (int($xmax/5)+1);
+        }
+    }
+    #
+    my $discdata .= '<data>'.join(',',@Labels).'</data>'.$/.
+                    '<data>'.join(',',@Disc).'</data>'.$/;
+    #
+    my $diffdata .= '<data>'.join(',',@Labels).'</data>'.$/.
+                    '<data>'.join(',',@Diff).'</data>'.$/;
+    #
+    my $title = 'Degree of Discrimination\nand Degree of Difficulty';
+    if ($xmax > 50) {
+        $title = 'Degree of Discrimination and Degree of Difficulty';
+    }
+    #
+    $plot=<<"END";
+<gnuplot 
+    texfont="10"
+    fgcolor="x000000"
+    plottype="Cartesian"
+    font="large"
+    grid="on"
+    align="center"
+    border="on"
+    transparent="on"
+    alttag="Degree of Discrimination and Degree of Difficulty Plot"
+    samples="100"
+    bgcolor="xffffff"
+    height="$height"
+    width="$width">
+    <key 
+        pos="top right"
+        title=""
+        box="off" />
+    <title>$title</title>
+    <axis xmin="0" ymin="$ymin" xmax="$xmax" ymax="$ymax" color="x000000" />
+    <xlabel>Problem Number</xlabel>
+    <curve 
+        linestyle="linespoints" 
+        name="DoDisc" 
+        pointtype="0" 
+        color="x000000">
+        $discdata
+    </curve>
+    <curve 
+        linestyle="linespoints" 
+        name="DoDiff" 
+        pointtype="0" 
+        color="xFF0000">
+        $diffdata
+    </curve>
+</gnuplot>
+END
+    my $plotresult = 
+        '<p>'.&Apache::lonxml::xmlparse($r,'web',$plot).'</p>'.$/;
+    $r->print($plotresult);
+    return;
 }
-=cut
 
+sub tries_data_plot {
+    my ($r)=@_;
+    my $count = scalar(@StatsArray);
+    my $width = 50 + 10*$count;
+    $width = 300 if ($width < 300);
+    my $height = 300;
+    my $plot = '';
+    my @STD;  my @Mean; my @Max; my @Min;
+    my @Labels;
+    my $ymax = 5;
+    foreach my $data (@StatsArray) {
+        my $max = $data->{'mean_tries'} + $data->{'std_tries'};
+        $ymax = $max if ($ymax < $max);
+        $ymax = $max if ($ymax < $max);
+        push(@Labels,$data->{'problem_num'});
+        push(@STD,$data->{'std_tries'});
+        push(@Mean,$data->{'mean_tries'});
+    }
+    #
+    # Make sure we show relevant information.
+    my $xmax = $Labels[-1];
+    if ($xmax > 50) {
+        if ($xmax % 10 != 0) {
+            $xmax = 10 * (int($xmax/10)+1);
+        }
+    } else {
+        if ($xmax % 5 != 0) {
+            $xmax = 5 * (int($xmax/5)+1);
+        }
+    }
+    $ymax = int($ymax)+1+2;
+    #
+    my $std_data .= '<data>'.join(',',@Labels).'</data>'.$/.
+                    '<data>'.join(',',@Mean).'</data>'.$/;
+    #
+    my $std_error_data .= '<data>'.join(',',@Labels).'</data>'.$/.
+                          '<data>'.join(',',@Mean).'</data>'.$/.
+                          '<data>'.join(',',@STD).'</data>'.$/;
+    #
+    my $title = 'Mean and S.D. of Tries';
+    if ($xmax > 25) {
+        $title = 'Mean and Standard Deviation of Tries';
+    }
+    #
+    $plot=<<"END";
+<gnuplot 
+    texfont="10"
+    fgcolor="x000000"
+    plottype="Cartesian"
+    font="large"
+    grid="on"
+    align="center"
+    border="on"
+    transparent="on"
+    alttag="Mean and S.D of Tries Plot"
+    samples="100"
+    bgcolor="xffffff"
+    height="$height"
+    width="$width">
+    <title>$title</title>
+    <axis xmin="0" ymin="0" xmax="$xmax" ymax="$ymax" color="x000000" />
+    <xlabel>Problem Number</xlabel>
+    <ylabel>Number of Tries</ylabel>
+    <curve 
+        linestyle="yerrorbars"
+        name="S.D. Tries" 
+        pointtype="1" 
+        color="x666666">
+        $std_error_data
+    </curve>
+    <curve 
+        linestyle="points"
+        name="Mean Tries" 
+        pointtype="1" 
+        color="xCC4444">
+        $std_data
+    </curve>
+</gnuplot>
+END
+    my $plotresult = 
+        '<p>'.&Apache::lonxml::xmlparse($r,'web',$plot).'</p>'.$/;
+    $r->print($plotresult);
+    return;
+}
 
-sub BuildStatisticsTable {
-    my ($cache,$upper,$lower,$list,$headings,$students,$r,$color)=@_;
-    my $NoElements = scalar @$list;
-    my @List=sort(@$list);
-
-#6666666
-#    my $file="/home/httpd/perl/tmp/183d.txt";
-#    open(OUT, ">$file");
-#6666666
-##     &Apache::lonstatistics::Create_PrgWin($r);
-##777777
-##    my (%Activity) = &LoadActivityLog();
-##    $r->print('<script>popwin.document.popremain.remaining.value="'.
-##              'Loading Discussion...";</script>');
-##    my ($doDiffFile) = &LoadDoDiffFile();
-
-##777777
-##    $Str .= &Classify($discriminantFactor, $students);
-
-    my $p_count = 0;
-    my $dummy;
-    my $p_val;
-    my $ResId;
-    my %GraphDat;
-    my $cIdx=0;
-
-    foreach my $sequence (split(':', $cache->{'orderedSequences'})) {
-        if($cache->{'ProblemStatisticsMaps'} ne 'All Maps'  &&
-           $cache->{'ProblemStatisticsMaps'} ne $cache->{$sequence.':title'}) {
+sub plot_dropdown {
+    my $current = '';
+    #
+    if (defined($env{'form.plot'})) {
+        $current = $env{'form.plot'};
+    }
+    #
+    my @Additional_Plots = (
+                            { graphable=>'yes',
+                              name => 'degrees',
+                              title => 'Difficulty Indexes' },
+                            { graphable=>'yes',
+                              name => 'tries statistics',
+                              title => 'Tries Statistics' });
+    #
+    my $Str= "\n".'<select name="plot" size="1">';
+    $Str .= '<option name="none"></option>'."\n";
+    $Str .= '<option name="none2">none</option>'."\n";
+    foreach my $field (@Additional_Plots,@Fields) {
+        if (! exists($field->{'graphable'}) ||
+            $field->{'graphable'} ne 'yes') {
             next;
         }
-        &CreateProblemStatisticsTableHeading($cache->{'DisplayFormat'}, 
-                                             $cache->{$sequence.':source'},
-                                             $cache->{$sequence.':title'}, 
-                                             $headings,$r);
-	my ($tar,$Tries,$Wrongs,$Code,$Disc)=split(/\&/,
-                                                   $List[$cIdx]);
-        my ($SqOrd,$PrOrd,$Prob)=split(/\:/,$tar);
-	$sequence+=100;
-	while ($SqOrd==$sequence && $cIdx<$NoElements) {
-	    my %storestats=();
-	    my $pOrd=$PrOrd;
-	    my $Temp = $Prob;
-	    my $MxTries = 0;
-	    my $TotalTries = 0;
-	    my $YES = 0;
-	    my $Incorrect = 0;
-	    my $Override = 0;
-	    my $StdNo = 0;
-	    my $DiscNo=0;
-	    my @StdLst;
-	    while ($pOrd==$PrOrd && $cIdx<$NoElements)
-	    {
-		$cIdx++;
-		$StdNo++;
-		$StdLst[ $StdNo ] = $Tries;
-		$TotalTries += $Tries;
-		if ( $MxTries < $Tries ) { $MxTries = $Tries; } 
-		if ( $Code eq 'C' ){ $YES++; }
-		elsif( $Code eq 'I' ) { $Incorrect++; }
-		elsif( $Code eq 'O' ) { $Override++; }
-		elsif( $Code eq '-' ) { $StdNo--; }
-		($tar,$Tries,$Wrongs,$Code,$Disc)=split(/\&/,
-                                                     $List[$cIdx]);
-	        ($SqOrd,$PrOrd,$Prob)=split(/\:/,$tar);
-	    }
-
-	    $p_count++;
-	    my $Dummy;
-	    ($ResId,$Dummy)=split(/\*/,$Temp);
-
-######################
-	    $Temp = '<a href="'.$cache->{$ResId.':source'}.
-                '" target="_blank">'.$cache->{$ResId.':title'}.$Dummy.'</a>';
-
-	    #$r->print('<br>rid='.$ResId);
-	    #$r->print('<br>src='.$cache->{$ResId.':source'});
-	    #$r->print('<br>tit='.$cache->{$ResId.':title'});
-
-	    my $res = &Apache::lonnet::declutter($cache->{$ResId.':source'});
-	    my $urlres=$res;
-
-	    $ResId=~/(\d+)\.(\d+)/;
-	    my $Map = &Apache::lonnet::declutter( $cache->{'map_id_'.$1} );
-	    $urlres=$Map;
-#######################
-
-#	    $res = '<a href="'.$cache->{$ResId.':source'}.'">'.$res.'</a>';
-	    #$Map = '<a href="'.$Map.'">'.$res.'</a>';
-
-#------------------------ Compute the Average of Tries about one problem
-	    my $Average = ($StdNo) ? $TotalTries/$StdNo : 0;
-
-	    $storestats{$ENV{'request.course.id'}.'___'.$urlres.'___timestamp'}=time;
-	    $storestats{$ENV{'request.course.id'}.'___'.$urlres.'___stdno'}=$StdNo;
-	    $storestats{$ENV{'request.course.id'}.'___'.$urlres.'___avetries'}=$Average;
-   
-#-------------------------------- Compute percentage of Wrong tries
-	    my $Wrong = ( $StdNo ) ? 100 * ( $Incorrect / $StdNo ) : 0;
-
-#-------------------------------- Compute Standard Deviation
-	    my $StdDev = 0; 
-	    if ( $StdNo > 1 ) {
-		for ( my $n = 0; $n < $StdNo; $n++ ) {
-		    my $Dif = $StdLst[ $n ]-$Average;
-		    $StdDev += $Dif*$Dif;
-		} 
-		$StdDev /= ( $StdNo - 1 );
-		$StdDev = sqrt( $StdDev );
-	    }
-
-#-------------------------------- Compute Degree of Difficulty
-	    my $DoDiff = 0;
-	    if( $TotalTries > 0 ) {
-		$DoDiff = 1 - ( ( $YES + $Override ) / $TotalTries );
-#	    $DoDiff =  ($TotalTries)/($YES + $Override+ 0.1);	    
-	    }
-       
-	    $storestats{$ENV{'request.course.id'}.'___'.$urlres.'___difficulty'}=$DoDiff;
-
-#-------------------------------- Compute the Skewness
-	    my $Skewness = 0;
-	    my $Sum = 0; 
-	    if ( $StdNo > 0 && $StdDev > 0 ) {
-		for ( my $n = 0; $n < $StdNo; $n++ ) {
-		    my $Dif = $StdLst[ $n ]-$Average;
-		    $Skewness += $Dif*$Dif*$Dif;
-		} 
-		$Skewness /= $StdNo;
-		$Skewness /= $StdDev*$StdDev*$StdDev;
-	    }
-
-#--------------------- Compute the Discrimination Factors
-            my ($Up1,$Up2)=split(/\:/,$upper->{$sequence.'@'.$pOrd});
-	    my ($Lw1,$Lw2)=split(/\:/,$lower->{$sequence.'@'.$pOrd});
-
-	    my $Dis1 = $Up1 - $Lw1;
-	    my $Dis2 = $Up2 - $Lw2;
-	    my $_D1 = sprintf("%.2f", $Dis1);
-	    my $_D2 = sprintf("%.2f", $Dis2);
-
-#-----------------  Some restition in presenting the float numbers
-	    my $Avg = sprintf( "%.2f", $Average );
-	    my $Wrng = sprintf( "%.1f", $Wrong );
-	    my $SD = sprintf( "%.1f", $StdDev );
-	    my $DoD = sprintf( "%.2f", $DoDiff );
-	    my $Sk = sprintf( "%.1f", $Skewness );
-	    my $join = $Prob.'&'.$Temp.'&'.$StdNo.'&'.
-                       $TotalTries.'&'.$MxTries.'&'.$Avg.'&'.
-                       $YES.'&'.$Override.'&'.$Wrng.'&'.$DoD.'&'.
-		       $SD.'&'.$Sk.'&'.$_D1.'&'.$_D2.'&'.
-                       $DiscNo.'&'.$Prob;
-
-#####{$sequence.'@'.$pOrd}
-	  #  $cache->{'tableCache:'.$p_count-1}=$join;
-
-#6666666
-#	    $r->print('<br>'.$out.'&'.$DoD);
-#            print (OUT $out.'@'.$DoD.'&');
-#6666666
-
-	    $urlres=~/^(\w+)\/(\w+)/;
-	    if ($StdNo) { 
-		&Apache::lonnet::put('resevaldata',\%storestats,$1,$2); 
-	    }
-#-------------------------------- Row of statistical table
-            &TableRow($cache,$join,$cIdx,($p_count-1),$r,$color,\%GraphDat);
-	}
-	&CloseTable($cache,$r);
-    }
-###    &Close_PrgWin();
-#666666
-#    close( OUT );
-#666666
+        $Str .= '<option value="'.$field->{'name'}.'"';
+        if ($field->{'name'} eq $current) {
+            $Str .= ' selected ';
+        }
+        $Str.= '>'.&mt($field->{'title'}).'</option>'."\n";
+    }
+    $Str .= '</select>'."\n";
+    return $Str;
 }
 
-=pod
-sub Cache_Statistics {
-    my ($cache,$color)=@_;
-    my @list = ();
-    my $Useful;
-    my $UnUseful;
-#    $r->print('<input type="hidden" name="show" value="excel" />'."\n"); 
-    my %myHeader = reverse( %Header );
-    $Pos = $myHeader{$ENV{'form.sort'}};
-    if ($Pos > 0) {$Pos++;}
-    my $p_count = 0;
-    foreach my $key( keys %CachData) { 
-	my @Temp=split(/\&/,$CachData{$key});
-	if ( $Pos == 0 ) {
-	    ($UnUseful,$Useful)=split(/\>/,$Temp[$Pos]);
-	}
-	else {
-	    $Useful = $Temp[$Pos];
-	}   
-	$list[$p_count]=$Useful.'@'.$CachData{$key};
-        $p_count++;
-    }
-
-    @list = sort MySort (@list);
-
-    my $nIndex=0;
-
-    if ( $Pos == 0 ) {
-	foreach (sort keys %mapsort) {
-	    my ($Hid,$pr)=split(/\:/,$mapsort{$_});
-	    &CreateProblemStatisticsTableHeading($cache,1,$Hid);
-	    my @lpr=split(/\&/,$pr);
-	    for (my $i=1; $i<=$#lpr; $i++) {
-		my($Pre, $Post) = split(/\@/,$list[$nIndex]); 
-		#$r->print('<br>'.$Pre.'---'.$Post);
-		&TableRow($cache,$Post,$i,$nIndex,$color,\%GraphDat);
-		$nIndex++;
-	    }
-	    &CloseTable($cache);
-	}
-    }
-    else {
-	&CreateProblemStatisticsTableHeading($cache,0);
-	for ( my $nIndex = 0; $nIndex < $p_count; $nIndex++ ) {
-	    my($Pre, $Post) = split(/\@/,$list[$nIndex]); 
-	    &TableRow($cache,$Post,$nIndex,$nIndex,$color,\%GraphDat);
-	} 
-	&CloseTable($cache);
-    }
-}
-=cut 
-
-sub TableRow {
-    my ($cache,$Str,$Idx,$RealIdx,$r,$color,$GraphDat)=@_;
-    my($PrOrd,$Temp,$StdNo,$TotalTries,$MxTries,$Avg,$YES,$Override,
-       $Wrng,$DoD,$SD,$Sk,$_D1,$_D2,$DiscNo,$Prob)=split(/\&/,$Str);	
-#    $r->print('<br>'.$Str);
-    my $Ptr;
-    if($cache->{'DisplayFormat'} eq 'Display CSV Format') {
-        my ($ResId,$Dummy)=split(/\*/,$Prob);
-        $Ptr="\n".'<br>'.
-             "\n".'"'.($RealIdx+1).'",'.
-             "\n".'"'.$cache->{$ResId.':title'}.$Dummy.'",'.
-             "\n".'"'.$cache->{$ResId.':source'}.'",'.
-             "\n".'"'.$StdNo.'",'.
-             "\n".'"'.$TotalTries.'",'.
-             "\n".'"'.$MxTries.'",'.
-             "\n".'"'.$Avg.'",'.
-             "\n".'"'.$YES.'",'.
-             "\n".'"'.$Override.'",'.
-             "\n".'"'.$Wrng.'",'.
-             "\n".'"'.$DoD.'",'.
-             "\n".'"'.$SD.'",'.
-             "\n".'"'.$Sk.'",'.
-             "\n".'"'.$_D1.'",'.
-	     "\n".'"'.$_D2.'"'.
-	     "\n".'"'.$DiscNo.'"';
-
-        $r->print("\n".$Ptr);
-    } else {
-        $Ptr="\n".'<tr>'.
-             "\n".'<td>'.($RealIdx+1).'</td>'.
-          #  "\n".'<td>'.$PrOrd.$Temp.'</td>'.
-             "\n".'<td>'.$Temp.'</td>'.
-             "\n".'<td bgcolor='.$color->{"yellow"}.'> '.$StdNo.'</td>'.
-             "\n".'<td bgcolor='.$color->{"yellow"}.'>'.$TotalTries.'</td>'.
-             "\n".'<td bgcolor='.$color->{"yellow"}.'>'.$MxTries.'</td>'.
-             "\n".'<td bgcolor='.$color->{"gb"}.'>'.$Avg.'</td>'.
-             "\n".'<td bgcolor='.$color->{"gb"}.'> '.$YES.'</td>'.
-             "\n".'<td bgcolor='.$color->{"gb"}.'> '.$Override.'</td>'.
-             "\n".'<td bgcolor='.$color->{"red"}.'> '.$Wrng.'</td>'.
-             "\n".'<td bgcolor='.$color->{"red"}.'> '.$DoD.'</td>'.
-             "\n".'<td bgcolor='.$color->{"green"}.'> '.$SD.'</td>'.
-             "\n".'<td bgcolor='.$color->{"green"}.'> '.$Sk.'</td>'.
-             "\n".'<td bgcolor='.$color->{"purple"}.'> '.$_D1.'</td>'.
-	     "\n".'<td bgcolor='.$color->{"purple"}.'> '.$_D2.'</td>'.
-             "\n".'<td bgcolor='.$color->{"yellow"}.'> '.$DiscNo.'</td>';
-        $r->print("\n".$Ptr.'</tr>' );
-    }
-#    $cache->{'graph_gif:'.$RealIdx}=$DoD.':'.$Wrng;
+###############################################
+###############################################
+##
+## Excel output routines
+##
+###############################################
+###############################################
+sub Excel_output {
+    my ($r) = @_;
+    $r->print('<h2>'.&mt('Preparing Excel Spreadsheet').'</h2>');
+    ##
+    ## Compute the statistics
+    &compute_all_statistics($r);
+    my $c = $r->connection;
+    return if ($c->aborted());
+    #
+    my ($starttime,$endtime) = &Apache::lonstathelpers::get_time_limits();
+    ##
+    ## Create the excel workbook
+    my ($excel_workbook,$filename,$format) =
+        &Apache::loncommon::create_workbook($r);
+    return if (! defined($excel_workbook));
+    #
+    # Add a worksheet
+    my $sheetname = $env{'course.'.$env{'request.course.id'}.'.description'};
+    if (length($sheetname) > 31) {
+        $sheetname = substr($sheetname,0,31);
+    }
+    my $excel_sheet = $excel_workbook->addworksheet(
+        &Apache::loncommon::clean_excel_name($sheetname));
+    ##
+    ## Begin creating excel sheet
+    ##
+    my ($rows_output,$cols_output) = (0,0);
+    #
+    # Put the course description in the header
+    $excel_sheet->write($rows_output,$cols_output++,
+                   $env{'course.'.$env{'request.course.id'}.'.description'},
+                        $format->{'h1'});
+    $cols_output += 3;
+    #
+    # Put a description of the sections listed
+    my $sectionstring = '';
+    $excel_sheet->write($rows_output,$cols_output++,
+                        &Apache::lonstatistics::section_and_enrollment_description('plaintext'),
+                        $format->{'h3'});
+    $cols_output += scalar(&Apache::lonstatistics::get_selected_sections());
+    $cols_output += scalar(&Apache::lonstatistics::get_selected_groups());
+    #
+    # Time restrictions
+    my $time_string;
+    if (defined($starttime)) {
+        # call localtime but not lonlocal:locallocaltime because excel probably
+        # cannot handle localized text.  Probably.
+        $time_string .= 'Data collected from '.localtime($time_string);
+        if (defined($endtime)) {
+            $time_string .= ' to '.localtime($endtime);
+        }
+        $time_string .= '.';
+    } elsif (defined($endtime)) {
+        # See note above about lonlocal:locallocaltime
+        $time_string .= 'Data collected before '.localtime($endtime).'.';
+    }
+    if (defined($time_string)) {
+        $excel_sheet->write($rows_output,$cols_output++,$time_string);
+        $cols_output+= 5;
+    }
+    #
+    # Put the date in there too
+    $excel_sheet->write($rows_output,$cols_output++,
+                        'Compiled on '.localtime(time));
+    #
+    $rows_output++; 
+    $cols_output=0;
+    ##
+    ## Sequence Statistics
+    ## 
+    &write_headers($excel_sheet,$format,\$rows_output,\$cols_output,
+                   \@SeqFields);
+    foreach my $seq (@sequences) {
+        my $data = $SeqStat{$seq->symb};
+        $cols_output=0;
+        foreach my $field (@SeqFields) {
+            next if ($field->{'selected'} ne 'yes');
+            my $fieldformat = undef;
+            if (exists($field->{'excel_format'})) {
+                $fieldformat = $format->{$field->{'excel_format'}};
+            }
+            $excel_sheet->write($rows_output,$cols_output++,
+                                $data->{$field->{'name'}},$fieldformat);
+        }
+        $rows_output++;
+        $cols_output=0;
+    }
+    ##
+    ## Resource Statistics
+    ##
+    $rows_output++;
+    $cols_output=0;
+    &write_headers($excel_sheet,$format,\$rows_output,\$cols_output,
+                   \@Fields);
+    #
+    foreach my $data (@StatsArray) {
+        $cols_output=0;
+        foreach my $field (@Fields) {
+            next if ($field->{'selected'} ne 'yes');
+            next if ($field->{'name'} eq 'problem_num');
+            my $fieldformat = undef;
+            if (exists($field->{'excel_format'})) {
+                $fieldformat = $format->{$field->{'excel_format'}};
+            }
+            $excel_sheet->write($rows_output,$cols_output++,
+                                $data->{$field->{'name'}},$fieldformat);
+        }
+        $rows_output++;
+        $cols_output=0;
+    }
+    #
+    $excel_workbook->close();
+    #
+    # Tell the user where to get their excel file
+    $r->print('<br />'.
+              '<a href="'.$filename.'">'.
+              &mt('Your Excel Spreadsheet').'</a>'."\n");
+    $r->rflush();
+    return;
 }
 
+##
+## &write_headers
+##
+sub write_headers {
+    my ($excel_sheet,$format,$rows_output,$cols_output,$Fields) = @_;
+    ##
+    ## First the long titles
+    foreach my $field (@{$Fields}) {
+        next if ($field->{'name'} eq 'problem_num');
+        next if ($field->{'selected'} ne 'yes');
+        if (exists($field->{'long_title'})) {
+            $excel_sheet->write($$rows_output,${$cols_output},
+                                $field->{'long_title'},
+                                $format->{'bold'});
+        } else {
+            $excel_sheet->write($$rows_output,${$cols_output},'');
+        }
+        ${$cols_output}+= 1;
+    }
+    ${$cols_output} =0;
+    ${$rows_output}+=1;
+    ##
+    ## Then the short titles
+    foreach my $field (@{$Fields}) {
+        next if ($field->{'selected'} ne 'yes');
+        next if ($field->{'name'} eq 'problem_num');
+        # Use english for excel as I am not sure how well excel handles 
+        # other character sets....
+        $excel_sheet->write($$rows_output,$$cols_output,
+                            $field->{'title'},
+                            $format->{'bold'});
+        $$cols_output+=1;
+    }
+    ${$cols_output} =0;
+    ${$rows_output}+=1;
+    return;
+}
 
-# For loading the colored table for display or un-colored for print
-sub setbgcolor {
-    my $PrintTable=shift;
-    my %color;
-    if ($PrintTable){
-	$color{"gb"}="#FFFFFF";
-	$color{"red"}="#FFFFFF";
-	$color{"yellow"}="#FFFFFF";
-	$color{"green"}="#FFFFFF";
-	$color{"purple"}="#FFFFFF";
-    } else {
-	$color{"gb"}="#DDFFFF";
-	$color{"red"}="#FFDDDD";
-	$color{"yellow"}="#EEFFCC";
-	$color{"green"}="#DDFFDD";
-	$color{"purple"}="#FFDDFF";
-    }
-
-    return \%color;
-}
-
-sub ProblemStatisticsButtons {
-    my ($displayFormat)=@_;
-
-    my $Ptr = '<tr><td></td><td align="left">';
-    $Ptr .= '<input type="submit" name="DoDiffGraph" ';
-    $Ptr .= 'value="DoDiff Graph" />'."\n";
-    $Ptr .= '&nbsp;&nbsp;&nbsp;';
-    $Ptr .= '<input type="submit" name="PercentWrongGraph" ';
-    $Ptr .= 'value="%Wrong Graph" />'."\n";
-    $Ptr .= '&nbsp;&nbsp;&nbsp;';
-    $Ptr .= '<input type="submit" name="DisplayCSVFormat" ';
-    if($displayFormat eq 'Display CSV Format') {
-        $Ptr .= 'value="Display Table Format" />'."\n";
-    } else {
-        $Ptr .= 'value="Display CSV Format" />'."\n";
+##################################################
+##################################################
+##
+## Statistics Gathering and Manipulation Routines
+##
+##################################################
+##################################################
+sub compute_statistics_on_sequence {
+    my ($seq) = @_;
+    my @Data;
+    foreach my $res (&Apache::lonstathelpers::get_resources($navmap,$seq)) {
+        foreach my $part (@{$res->parts}) {
+            next if ($res->is_survey($part));
+            #
+            # This is where all the work happens
+            my $data = &get_statistics($seq,$res,$part,scalar(@StatsArray)+1);
+            push (@Data,$data);
+            push (@StatsArray,$data);
+        }
     }
-    $Ptr .= '</td></tr>';
+    return @Data;
+}
 
-    return $Ptr;
+sub compute_all_statistics {
+    my ($r) = @_;
+    if (@StatsArray > 0) {
+        # Assume we have already computed the statistics
+        return;
+    }
+    my $c = $r->connection;
+    foreach my $seq (@sequences) {
+        last if ($c->aborted);
+        &compute_sequence_statistics($seq);
+        &compute_statistics_on_sequence($seq);
+    }
 }
 
-sub ProblemStatisticsLegend {
-    my $Ptr = '';
-    $Ptr = '<table border="0">';
-    $Ptr .= '<tr><td>';
-    $Ptr .= '<b>#Stdnts</b></td>';
-    $Ptr .= '<td>Total Number of Students opened the problem.';
-    $Ptr .= '</td></tr><tr><td>';
-    $Ptr .= '<b>Tries</b></td>';
-    $Ptr .= '<td>Total Number of Tries for solving the problem.';
-    $Ptr .= '</td></tr><tr><td>';
-    $Ptr .= '<b>Mod</b></td>';
-    $Ptr .= '<td>Maximunm Number of Tries for solving the problem.';
-    $Ptr .= '</td></tr><tr><td>';
-    $Ptr .= '<b>Mean</b></td>';
-    $Ptr .= '<td>Average Number of the tries. [ Tries / #Stdnts ]';
-    $Ptr .= '</td></tr><tr><td>';
-    $Ptr .= '<b>#YES</b></td>';
-    $Ptr .= '<td>Number of students solved the problem correctly.';
-    $Ptr .= '</td></tr><tr><td>';
-    $Ptr .= '<b>#yes</b></td>';
-    $Ptr .= '<td>Number of students solved the problem by override.';
-    $Ptr .= '</td></tr><tr><td>';
-    $Ptr .= '<b>%Wrng</b></td>';
-    $Ptr .= '<td>Percentage of students tried to solve the problem ';
-    $Ptr .= 'but still incorrect. [ 100*((#Stdnts-(#YES+#yes))/#Stdnts) ]';
-    $Ptr .= '</td></tr><tr><td>';
-    $Ptr .= '<b>DoDiff</b></td>';
-    $Ptr .= '<td>Degree of Difficulty of the problem.  ';
-    $Ptr .= '[ 1 - ((#YES+#yes) / Tries) ]';
-    $Ptr .= '</td></tr><tr><td>';
-    $Ptr .= '<b>S.D.</b></td>';
-    $Ptr .= '<td>Standard Deviation of the tries.  ';
-    $Ptr .= '[ sqrt(sum((Xi - Mean)^2)) / (#Stdnts-1) ';
-    $Ptr .= 'where Xi denotes every student\'s tries ]';
-    $Ptr .= '</td></tr><tr><td>';
-    $Ptr .= '<b>Skew.</b></td>';
-    $Ptr .= '<td>Skewness of the students tries.';
-    $Ptr .= '[(sqrt( sum((Xi - Mean)^3) / #Stdnts)) / (S.D.^3)]';
-    $Ptr .= '</td></tr><tr><td>';
-    $Ptr .= '<b>Dis.F.</b></td>';
-    $Ptr .= '<td>Discrimination Factor: A Standard for evaluating the ';
-    $Ptr .= 'problem according to a Criterion<br>';
-    $Ptr .= '<b>[Applied Criterion in %27 Upper Students - ';
-    $Ptr .= 'Applied the same Criterion in %27 Lower Students]</b><br>';
-    $Ptr .= '<b>1st Criterion</b> for Sorting the Students: ';
-    $Ptr .= '<b>Sum of Partial Credit Awarded / Total Number of Tries</b><br>';
-    $Ptr .= '<b>2nd Criterion</b> for Sorting the Students: ';
-    $Ptr .= '<b>Total number of Correct Answers / Total Number of Tries</b>';
-    $Ptr .= '</td></tr>';
-    $Ptr .= '<tr><td><b>Disc.</b></td>';
-    $Ptr .= '<td>Number of Students had at least one discussion.';
-    $Ptr .= '</td></tr></table>';
-
-    return $Ptr;
-}
-
-#------- Processing upperlist and lowerlist according to each problem
-sub ProcessDiscriminant {
-    my ($List,$r) = @_;
-    my @sortedList = sort (@$List);
-    my $Count = scalar @sortedList;
-    my $Problem;
-    my @Dis;
-    my $Slvd=0;
-    my $tmp;
-    my $Sum1=0;
-    my $Sum2=0;
-    my $nIndex=0;
-    my $nStudent=0;
-    my %Proc=undef;
-    while ($nIndex<$Count) {
-#        $r->print("<br> $nIndex) $sortedList[$nIndex]");
-	($Problem,$tmp)=split(/\=/,$sortedList[$nIndex]);
-	@Dis=split(/\+/,$tmp);
-	my $Temp = $Problem;
-	do {
-	    $nIndex++;
-	    $nStudent++;
-	    $Sum1 += $Dis[0];
-	    $Sum2 += $Dis[1];
-	    ($Problem,$tmp)=split(/\=/,$sortedList[$nIndex]);
-	    @Dis=split(/\+/,$tmp);
-	} while ( $Problem eq $Temp && $nIndex < $Count );
-	$Proc{$Temp}=($Sum1/$nStudent).':'.($Sum2/$nStudent);
-#        $r->print("<br> $nIndex) $Temp --> ($nStudent) $Proc{$Temp}");
-	$Sum1=0;
-	$Sum2=0;
-	$nStudent=0;
-    }
-
-    return %Proc;
-}
-
-#------- Creating Discimination factor   
-sub Discriminant {
-    my ($discriminant,$r)=@_;
-#$Apache::lonxml::debug=1;
-#&Apache::lonhomework::showhash(%$discriminant);
-#$Apache::lonxml::debug=0;
-    my @discriminantKeys=keys(%$discriminant);
-    my $Count = scalar @discriminantKeys;
-
-    my $UpCnt = int(0.27*$Count);
-    my $low=0;
-    my $up=$Count-$UpCnt;
-    my @UpList=();
-    my @LowList=();
-
-    $Count=0;
-    foreach my $key (sort(@discriminantKeys)) { 
-	$Count++;    
-	if($low < $UpCnt || $Count > $up) {
-            $low++;
-            my $str=$discriminant->{$key};
-            foreach(split(/\&/,$str)){
-                if($_) {
-                    if($low<$UpCnt) { push(@LowList,$_); }
-                    else            { push(@UpList,$_);  }
+sub sort_data {
+    my ($sortkey) = @_;
+    return if (! @StatsArray);
+    #
+    # Sort the data
+    my $sortby = undef;
+    foreach my $field (@Fields) {
+        if ($sortkey eq $field->{'name'}) {
+            $sortby = $field->{'name'};
+        }
+    }
+    if (! defined($sortby) || $sortby eq '' || $sortby eq 'problem_num') {
+        $sortby = 'container';
+    }
+    if ($sortby ne 'container') {
+        # $sortby is already defined, so we can charge ahead
+        if ($sortby =~ /^(title|part)$/i) {
+            # Alpha comparison
+            @StatsArray = sort {
+                lc($a->{$sortby}) cmp lc($b->{$sortby}) ||
+                lc($a->{'title'}) cmp lc($b->{'title'}) ||
+                lc($a->{'part'}) cmp lc($b->{'part'});
+            } @StatsArray;
+        } else {
+            # Numerical comparison
+            @StatsArray = sort {
+                my $retvalue = 0;
+                if ($b->{$sortby} eq 'nan') {
+                    if ($a->{$sortby} ne 'nan') {
+                        $retvalue = -1;
+                    } else {
+                        $retvalue = 0;
+                    }
                 }
-            }
+                if ($a->{$sortby} eq 'nan') {
+                    if ($b->{$sortby} ne 'nan') {
+                        $retvalue = 1;
+                    }
+                }
+                if ($retvalue eq '0') {
+                    $retvalue = $b->{$sortby} <=> $a->{$sortby}     ||
+                            lc($a->{'title'}) <=> lc($b->{'title'}) ||
+                            lc($a->{'part'})  <=> lc($b->{'part'});
+                }
+                $retvalue;
+            } @StatsArray;
         }
     }
-    my %DisUp =  &ProcessDiscriminant(\@UpList,$r);
-    my %DisLow = &ProcessDiscriminant(\@LowList,$r);
+    #
+    # Renumber the data set
+    my $count;
+    foreach my $data (@StatsArray) {
+        $data->{'problem_num'} = ++$count;
+    }
+    return;
+}
 
-    return (\%DisUp, \%DisLow);
-}   
+########################################################
+########################################################
 
-#---- END Problem Statistics Web Page ----------------------------------------
+=pod
 
-#---- Problem Statistics Graph Web Page --------------------------------------
+=item &get_statistics()
 
-# ------------------------------------------- Prepare data for Graphical chart
+Wrapper routine from the call to loncoursedata::get_problem_statistics.  
+Calls lonstathelpers::get_time_limits() to limit the data set by time
+and &compute_discrimination_factor
 
-sub BuildDiffGraph {
-    my ($r)=@_;
+Inputs: $sequence, $resource, $part, $problem_num
 
-    my $graphData = &GetGraphData('DiffGraph', $r);
-    $r->print('<IMG src="/cgi-bin/graph.gif?'.$graphData.'" />');
+Returns: Hash reference with statistics data from 
+loncoursedata::get_problem_statistics.
 
-    return;
+=cut
+
+########################################################
+########################################################
+sub get_statistics {
+    my ($sequence,$resource,$part,$problem_num) = @_;
+    #
+    my ($starttime,$endtime) = &Apache::lonstathelpers::get_time_limits();
+    my $symb = $resource->symb;
+    my $courseid = $env{'request.course.id'};
+    #
+    my $data = &Apache::loncoursedata::get_problem_statistics
+                        ([&Apache::lonstatistics::get_selected_sections()],
+                         [&Apache::lonstatistics::get_selected_groups()],
+                         $Apache::lonstatistics::enrollment_status,
+                         $symb,$part,$courseid,$starttime,$endtime);
+    $data->{'symb'}        = $symb;
+    $data->{'part'}        = $part;
+    $data->{'problem_num'} = $problem_num;
+    $data->{'container'}   = $sequence->compTitle;
+    $data->{'title'}       = $resource->compTitle;
+    $data->{'title.link'}  = $resource->src.'?symb='.
+        &escape($resource->symb);
+    #
+    if ($SelectedFields{'deg_of_disc'}) {
+        $data->{'deg_of_disc'} = 
+            &compute_discrimination_factor($resource,$part,$sequence);
+    }
+    #
+    # Store in metadata if computations were done for all students
+    if ($data->{'num_students'} > 1) {
+        my @Sections = &Apache::lonstatistics::get_selected_sections();
+        my $sections = '"'.join(' ',@Sections).'"';
+        $sections =~ s/&+/_/g;  # Ensure no special characters
+        $data->{'sections'}=$sections;
+        $data->{'course'} = $env{'request.course.id'};
+        my $urlres=(&Apache::lonnet::decode_symb($resource->symb))[2];
+        $data->{'urlres'}=$urlres;
+        my %storestats = 
+            &LONCAPA::lonmetadata::dynamic_metadata_storage($data);
+        my ($dom,$user) = ($urlres=~m{^($LONCAPA::domain_re)/($LONCAPA::username_re)}); 
+        &Apache::lonnet::put('nohist_resevaldata',\%storestats,$dom,$user);
+    }
+    #
+    $data->{'tries_per_correct'} = $data->{'tries'} / 
+        ($data->{'num_solved'}+0.1);
+    #
+    # Get the due date for research purposes (commented out most of the time)
+#    $data->{'duedate'} = 
+#        &Apache::lonnet::EXT('resource.'.$part.'.duedate',$symb);
+#    $data->{'opendate'} = 
+#        &Apache::lonnet::EXT('resource.'.$part.'.opendate',$symb);
+#    $data->{'maxtries'} = 
+#        &Apache::lonnet::EXT('resource.'.$part.'.maxtries',$symb);
+#    $data->{'hinttries'} =
+#        &Apache::lonnet::EXT('resource.'.$part.'.hinttries',$symb);
+    $data->{'weight'} =
+        &Apache::lonnet::EXT('resource.'.$part.'.weight',$symb);
+#    $data->{'resptypes'} = join(',',@{$resource->{'partdata'}->{$part}->{'ResponseTypes'}});
+    return $data;
 }
 
-sub BuildWrongGraph {
-    my ($r)=@_;
+###############################################
+###############################################
 
-    my $graphData = &GetGraphData('WrongGraph', $r);
-    $r->print('<IMG src="/cgi-bin/graph.gif?'.$graphData.'" />');
+=pod
 
-    return;
-}
+=item &compute_discrimination_factor()
+
+Inputs: $Resource, $Sequence
 
+Returns: integer between -1 and 1
+
+=cut
+
+###############################################
+###############################################
+sub compute_discrimination_factor {
+    my ($resource,$part,$seq) = @_;
+    my $symb = $resource->symb;
+    my @Resources;
+    foreach my $res (&Apache::lonstathelpers::get_resources($navmap,$seq)){
+        next if ($res->symb eq $symb);
+        push (@Resources,$res->symb);
+    }
+    #
+    # rank
+    my ($starttime,$endtime) = &Apache::lonstathelpers::get_time_limits();
+    my $ranking = 
+        &Apache::loncoursedata::rank_students_by_scores_on_resources
+        (\@Resources,
+         [&Apache::lonstatistics::get_selected_sections()],
+         [&Apache::lonstatistics::get_selected_groups()],
+         $Apache::lonstatistics::enrollment_status,undef,
+         $starttime,$endtime, $symb);
+    #
+    # compute their percent scores on the problems in the sequence,
+    my $number_to_grab = int(scalar(@{$ranking})/4);
+    my $num_students = scalar(@{$ranking});
+    my @BottomSet = map { $_->[&Apache::loncoursedata::RNK_student()]; 
+                      } @{$ranking}[0..$number_to_grab];
+    my @TopSet    = 
+        map { 
+            $_->[&Apache::loncoursedata::RNK_student()]; 
+          } @{$ranking}[-$number_to_grab..0];
+    if (! @BottomSet || (@BottomSet == 1 && $BottomSet[0] eq '') ||
+        ! @TopSet    || (@TopSet    == 1 && $TopSet[0]    eq '')) {
+        return 'nan';
+    }
+    my ($bottom_sum,$bottom_max) = 
+        &Apache::loncoursedata::get_sum_of_scores($symb,$part,\@BottomSet,
+                                                  undef,$starttime,$endtime);
+    my ($top_sum,$top_max) = 
+        &Apache::loncoursedata::get_sum_of_scores($symb,$part,\@TopSet,
+                                                  undef,$starttime,$endtime);
+    my $deg_of_disc;
+    if ($top_max == 0 || $bottom_max==0) {
+        $deg_of_disc = 'nan';
+    } else {
+        $deg_of_disc = ($top_sum/$top_max) - ($bottom_sum/$bottom_max);
+    }
+    #&Apache::lonnet::logthis('    '.$top_sum.'/'.$top_max.
+    #                         ' - '.$bottom_sum.'/'.$bottom_max);
+    return $deg_of_disc;
+}
 
-sub GetGraphData {
-    my ($ylab,$r,%GraphDat)=@_;
-    my $Col;
-    my $data='';
-    my $count = 0;
-    my $Max = 0;
-    my $cid=$ENV{'request.course.id'};
-    my $GraphDB = "/home/httpd/perl/tmp/$ENV{'user.name'}".
-                  "_$ENV{'user.domain'}_$cid\_graph.db";
-    foreach (keys %GraphDat) {delete $GraphDat{$_};}
-    if (-e "$GraphDB") {
-	if (tie(%GraphDat,'GDBM_File',"$GraphDB",&GDBM_READER,0640)) {
-	    if ( $ylab eq 'DoDiff Graph' ) {
-		$ylab = 'Degree-of-Difficulty';
-		$Col = 0;
-	    }
-	    else {
-		$ylab = 'Wrong-Percentage';
-		$Col = 1;
-	    }
-	    foreach (sort NumericSort keys %GraphDat) { 
-		my @Temp=split(/\:/,$GraphDat{$_});
-                my $inf = $Temp[$Col]; 
-		if ( $Max < $inf ) {$Max = $inf;}
-		$data .= $inf.',';
-		$count++;
-	    }
-	    if ( $Max > 1 ) { 
-		$Max += (10 - $Max % 10);
-		$Max = int($Max);
-	    }
-	    else { $Max = 1; }
-            untie(%GraphDat);
-	    my $Course = $ENV{'course.'.$cid.'.description'};
-	    $Course =~ s/\ /"_"/eg;
-	    my $GData=$Course.'&'.'Problems'.'&'.$ylab.'&'.
-		      $Max.'&'.$count.'&'.$data;
-	}
-	else {
-	    $r->print("Unable to tie hash to db file");
-	}
+###############################################
+###############################################
+##
+## Compute KR-21
+##
+## To compute KR-21, you need the following information:
+##
+## K=the number of items in your test
+## M=the mean score on the test
+## s=the standard deviation of the scores on your test 
+##
+## then:
+## 
+## KR-21 rk= [K/(K-1)] * [1- (M*(K-M))/(K*s^2))]
+##
+###############################################
+###############################################
+sub compute_sequence_statistics {
+    my ($seq) = @_;
+    my $symb = $seq->symb;
+    my @Resources;
+    my $part_count;
+    foreach my $res (&Apache::lonstathelpers::get_resources($navmap,$seq)) {
+        push (@Resources,$res->symb);
+        $part_count += scalar(@{$res->parts});
+    }
+    my ($starttime,$endtime) = &Apache::lonstathelpers::get_time_limits();
+    #
+    # First compute statistics based on student scores
+    my ($smin,$smax,$sMean,$sSTD,$scount,$sMAX) = 
+        &Apache::loncoursedata::score_stats
+                    ([&Apache::lonstatistics::get_selected_sections()],
+                     [&Apache::lonstatistics::get_selected_groups()],
+                     $Apache::lonstatistics::enrollment_status,
+                     \@Resources,$starttime,$endtime,undef);
+    $SeqStat{$symb}->{'title'}  = $seq->compTitle;
+    $SeqStat{$symb}->{'scoremax'}  = $smax;
+    $SeqStat{$symb}->{'scoremin'}  = $smin;
+    $SeqStat{$symb}->{'scoremean'} = $sMean;
+    $SeqStat{$symb}->{'scorestd'}  = $sSTD;
+    $SeqStat{$symb}->{'scorecount'} = $scount;
+    $SeqStat{$symb}->{'max_possible'} = $sMAX;
+    #
+    # Compute statistics based on the number of correct problems
+    # 'correct' is taken to mean 
+    my ($cmin,$cmax,$cMean,$cSTD,$ccount)=
+        &Apache::loncoursedata::count_stats
+        ([&Apache::lonstatistics::get_selected_sections()],
+         [&Apache::lonstatistics::get_selected_groups()],
+         $Apache::lonstatistics::enrollment_status,
+         \@Resources,$starttime,$endtime,undef);
+    my $K = $part_count;
+    my $kr_21;
+    if ($K > 1 && $cSTD > 0) {
+        $kr_21 =  ($K/($K-1)) * (1 - $cMean*($K-$cMean)/($K*$cSTD**2));
+    } else {
+        $kr_21 = 'nan';
     }
+    $SeqStat{$symb}->{'countmax'} = $cmax;
+    $SeqStat{$symb}->{'countmin'} = $cmin;
+    $SeqStat{$symb}->{'countstd'} = $cSTD;
+    $SeqStat{$symb}->{'countmean'} = $cMean;
+    $SeqStat{$symb}->{'count'} = $ccount;
+    $SeqStat{$symb}->{'items'} = $K;
+    $SeqStat{$symb}->{'KR-21'}=$kr_21;
+    return;
 }
 
 
+
+=pod 
+
+=item ProblemStatisticsLegend
+
+=over 4
+
+=item #Stdnts
+Total number of students attempted the problem.
+
+=item Tries
+Total number of tries for solving the problem.
+
+=item Max Tries
+Largest number of tries for solving the problem by a student.
+
+=item Mean
+Average number of tries. [ Tries / #Stdnts ]
+
+=item #YES
+Number of students solved the problem correctly.
+
+=item #yes
+Number of students solved the problem by override.
+
+=item %Wrong
+Percentage of students who tried to solve the problem 
+but is still incorrect. [ 100*((#Stdnts-(#YES+#yes))/#Stdnts) ]
+
+=item DoDiff
+Degree of Difficulty of the problem.  
+[ 1 - ((#YES+#yes) / Tries) ]
+
+=item S.D.
+Standard Deviation of the tries.  
+[ sqrt(sum((Xi - Mean)^2)) / (#Stdnts-1) 
+where Xi denotes every student\'s tries ]
+
+=item Skew.
+Skewness of the students tries.
+[(sqrt( sum((Xi - Mean)^3) / #Stdnts)) / (S.D.^3)]
+
+=item Dis.F.
+Discrimination Factor: A Standard for evaluating the 
+problem according to a Criterion<br>
+
+=item [Criterion to group students into %27 Upper Students - 
+and %27 Lower Students]
+1st Criterion for Sorting the Students: 
+Sum of Partial Credit Awarded / Total Number of Tries
+2nd Criterion for Sorting the Students: 
+Total number of Correct Answers / Total Number of Tries
+
+=item Disc.
+Number of Students had at least one discussion.
+
+=back
+
+=cut
+
+############################################################
+############################################################
+
 1;
 __END__