--- loncom/interface/statistics/lonproblemstatistics.pm	2002/08/14 21:51:51	1.28
+++ loncom/interface/statistics/lonproblemstatistics.pm	2003/03/28 15:20:59	1.48
@@ -1,7 +1,6 @@
 # The LearningOnline Network with CAPA
-# (Publication Handler
 #
-# $Id: lonproblemstatistics.pm,v 1.28 2002/08/14 21:51:51 stredwic Exp $
+# $Id: lonproblemstatistics.pm,v 1.48 2003/03/28 15:20:59 matthew Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -26,445 +25,845 @@
 # 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
-# 5/12,5/14,5/15,5/19,5/26,7/16,7/25,7/29,8/5  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::lonhtmlcommon;
 use Apache::loncoursedata;
-use GDBM_File;
+use Apache::lonstatistics;
+use Spreadsheet::WriteExcel;
 
-my $jr;
+###############################################
+###############################################
 
-sub InitializeProblemStatistics {
-    my ($cacheDB, $students, $courseID, $c, $r)=@_;
-    my %cache;
-
-    $jr = $r;
-
-    unless(tie(%cache,'GDBM_File',$cacheDB,&GDBM_READER(),0640)) {
-        $r->print('Unable to tie database1.');
-        return ('ERROR', undef);
-    }
-
-    # Remove students who don't have the proper section.
-    my @sectionsSelected = split(':',$cache{'sectionsSelected'});
-    for(my $studentIndex=((scalar @$students)-1); $studentIndex>=0;
-        $studentIndex--) {
-        my $value = $cache{$students->[$studentIndex].':section'};
-        my $found = 0;
-        foreach (@sectionsSelected) {
-            if($_ eq 'none') {
-                if($value eq '' || !defined($value) || $value eq ' ') {
-                    $found = 1;
-                    last;
-                }
-            } else {
-                if($value eq $_) {
-                    $found = 1;
-                    last;
-                }
-            }
-        }
-        if($found == 0) {
-            splice(@$students, $studentIndex, 1);
-        }
-    }
+=pod 
 
-    my $isNotCached = 0;
-    my $lastStatus = (defined($cache{'StatisticsLastStatus'})) ?
-                     $cache{'StatisticsLastStatus'} : 'Nothing';
-    my $whichStudents = join(':::',sort(@$students));
-    if(!defined($cache{'StatisticsCached'}) || 
-       $lastStatus ne $cache{'Status'} ||
-       $whichStudents ne $cache{'StatisticsWhichStudents'}) {
-        $isNotCached = 1;
-    }
+=item &CreateInterface()
+
+Create the main intereface for the statistics page.  Allows the user to
+select sections, maps, and output.
+
+=cut
+
+###############################################
+###############################################
+sub CreateInterface {
+    my $Str = '';
+    $Str .= '<table cellspacing="5">'."\n";
+    $Str .= '<tr>';
+    $Str .= '<td align="center"><b>Sections</b></td>';
+    $Str .= '<td align="center"><b>Sequences and Folders</b></td>';
+    $Str .= '<td align="center"><b>Output</b></td>';
+    $Str .= '</tr>'."\n";
+    #
+    $Str .= '<tr><td align="center">'."\n";
+    $Str .= &Apache::lonstatistics::SectionSelect('Section','multiple',5);
+    $Str .= '</td><td align="center">';
+    #
+    my $only_seq_with_assessments = sub { 
+        my $s=shift;
+        if ($s->{'num_assess'} < 1) { 
+            return 0;
+        } else { 
+            return 1;
+        }
+    };
+    $Str .= &Apache::lonstatistics::MapSelect('Maps','multiple,all',5,
+                                              $only_seq_with_assessments);
+    $Str .= '</td><td>'."\n";
+    $Str .= &CreateAndParseOutputSelector();
+    $Str .= '</td></tr>'."\n";
+    $Str .= '</table>'."\n";
+    return $Str;
+}
 
-    untie(%cache);
-    unless(tie(%cache,'GDBM_File',$cacheDB,&GDBM_WRCREAT(),0640)) {
-        $r->print('Unable to tie database.2');
-        return ('ERROR', undef);
-    }
-    if($isNotCached && defined($cache{'StatisticsCached'})) {
-        my @statkeys = split(':::', $cache{'StatisticsKeys'});
-        delete $cache{'StatisticsKeys'};
-        delete $cache{'StatisticsCached'};
-        foreach(@statkeys) {
-            delete $cache{$_};
-        }
-    }
+#######################################################
+#######################################################
 
-    untie(%cache);
-    if($isNotCached) {
-        &Apache::loncoursedata::DownloadStudentCourseDataSeparate($students,
-                                                                  'true',
-                                                                  $cacheDB,
-                                                                  'true', 
-                                                                  'true',
-                                                                  $courseID,
-                                                                  $r, $c);
-    }
-    if($c->aborted()) { return ('ERROR', undef); }
+=pod
 
-    unless(tie(%cache,'GDBM_File',$cacheDB,&GDBM_READER(),0640)) {
-        $r->print('Unable to tie database.3');
-        return ('ERROR', undef);
-    }
-    my $problemData;
-    if($isNotCached) {
-        ($problemData) = &ExtractStudentData(\%cache, $students);
-        &CalculateStatistics($problemData, \%cache);
-    }
-    untie(%cache);
+=item &CreateAndParseOutputSelector()
 
-    unless(tie(%cache,'GDBM_File',$cacheDB,&GDBM_WRCREAT(),0640)) {
-        $r->print('Unable to tie database.4');
-        return ('ERROR', undef);
+Construct a selection list of options for output and parse output selections.
+The current output selected is indicated by the values of the two package
+variables $output_mode and $show.  @OutputOptions holds the descriptions of
+the output options and the values for $output_mode and $show.
+
+ Based on code from lonstudentassessment.pm.
+
+=cut
+
+#######################################################
+#######################################################
+my $output_mode;
+my $show;
+
+my @OutputOptions = 
+    (
+     { name  => 'problem statistics grouped by sequence',
+       value => 'HTML problem statistics grouped',
+       description => 'Output statistics for the problem parts.',
+       mode => 'html',
+       show => 'grouped',
+     },
+     { name  => 'problem statistics ungrouped',
+       value => 'HTML problem statistics ungrouped',
+       description => 'Output statistics for the problem parts.',
+       mode => 'html',
+       show => 'ungrouped',
+     },
+     { name  => 'problem statistics, Excel',
+       value => 'Excel problem statistics',
+       description => 'Output statistics for the problem parts '.
+           'in an Excel workbook',
+       mode => 'excel',
+       show => 'all',
+     },
+     { name  => 'Degree of Difficulty Plot',
+       value => 'plot deg diff',
+       description => 'Generate a plot of the degree of difficulty of each '.
+           'problem part.',
+       mode => 'plot',
+       show => 'deg of diff',
+     },
+     { name  => 'Percent Wrong Plot',
+       value => 'plot per wrong',
+       description => 'Generate a plot showing the percent of students who '.
+           'were unable to complete each problem part',
+       mode => 'plot',
+       show => 'per wrong',
+     },
+     );
+
+sub OutputDescriptions {
+    my $Str = '';
+    $Str .= "<h2>Output Modes</h2>\n";
+    $Str .= "<dl>\n";
+    foreach my $outputmode (@OutputOptions) {
+	$Str .="    <dt>".$outputmode->{'name'}."</dt>\n";
+	$Str .="        <dd>".$outputmode->{'description'}."</dd>\n";
     }
-    if($isNotCached) {
-        foreach(keys(%$problemData)) {
-            $cache{$_} = $problemData->{$_};
+    $Str .= "</dl>\n";
+    return $Str;
+}
+
+sub CreateAndParseOutputSelector {
+    my $Str = '';
+    my $elementname = 'statsoutputmode';
+    #
+    # Format for output options is 'mode, restrictions';
+    my $selected = 'HTML problem statistics grouped';
+    if (exists($ENV{'form.'.$elementname})) {
+        if (ref($ENV{'form.'.$elementname} eq 'ARRAY')) {
+            $selected = $ENV{'form.'.$elementname}->[0];
+        } else {
+            $selected = $ENV{'form.'.$elementname};
         }
-        $cache{'StatisticsKeys'} = join(':::', keys(%$problemData));
-        $cache{'StatisticsCached'} = 'true';
-        $cache{'StatisticsLastStatus'} = $cache{'Status'};
-        $cache{'StatisticsWhichStudents'} = $whichStudents;
     }
-    untie(%cache);
-
-    unless(tie(%cache,'GDBM_File',$cacheDB,&GDBM_READER(),0640)) {
-        $r->print('Unable to tie database.5');
-        return ('ERROR', undef);
+    #
+    # Set package variables describing output mode
+    $output_mode = 'html';
+    $show        = 'all';
+    foreach my $option (@OutputOptions) {
+        next if ($option->{'value'} ne $selected);
+        $output_mode = $option->{'mode'};
+        $show        = $option->{'show'};
+    }
+    #
+    # Build the form element
+    $Str = qq/<select size="5" name="$elementname">/;
+    foreach my $option (@OutputOptions) {
+        $Str .= "\n".'    <option value="'.$option->{'value'}.'"';
+        $Str .= " selected " if ($option->{'value'} eq $selected);
+        $Str .= ">".$option->{'name'}."<\/option>";
     }
+    $Str .= "\n</select>";
+    return $Str;
+}
 
-    my $orderedProblems = &SortProblems(\%cache, 
-                                        $cache{'ProblemStatisticsSort'},
-                                        $cache{'SortProblems'},
-                                        $cache{'ProblemStatisticsAscend'});
-    untie(%cache);
+###############################################
+###############################################
 
-    return ('OK', $orderedProblems);
-}
+=pod 
 
-sub BuildProblemStatisticsPage {
-    my ($cacheDB, $students, $courseID, $c, $r)=@_;
+=item &Gather_Student_Data()
 
-    my @Header = ("Homework Sets Order","#Stdnts","Tries","Mod",
-                  "Mean","#YES","#yes","%Wrng","DoDiff",
-                  "S.D.","Skew.","D.F.1st","D.F.2nd");
-    my $color=&setbgcolor(0);
-    my %cache;
+Ensures all student data is up to date.
 
-    unless(tie(%cache,'GDBM_File',$cacheDB,&GDBM_READER(),0640)) {
-        $r->print('Unable to tie database.6');
-        return;
+=cut
+
+###############################################
+###############################################
+sub Gather_Student_Data {
+    my ($r) = @_;
+    my $c = $r->connection();
+    #
+    my @Sequences = &Apache::lonstatistics::Sequences_with_Assess();
+    #
+    my @Students = @Apache::lonstatistics::Students;
+    #
+    # Open the progress window
+    my %prog_state=&Apache::lonhtmlcommon::Create_PrgWin
+        ($r,'Statistics Compilation Status',
+         'Statistics Compilation Progress', scalar(@Students));
+    #
+    while (my $student = shift @Students) {
+        return if ($c->aborted());
+        my ($status,undef) = &Apache::loncoursedata::ensure_current_data
+            ($student->{'username'},$student->{'domain'},
+             $ENV{'request.course.id'});
+        &Apache::lonhtmlcommon::Increment_PrgWin($r,\%prog_state,
+                                                 'last student');
     }
-    my $Ptr = '';
-    $Ptr .= '<table border="0" cellspacing="5"><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 .= '<tr><td align="right"><b>Select Sections</b>';
-    $Ptr .= '</td>'."\n";
-    $Ptr .= '<td align="left">'."\n";
-    my @sections = split(':',$cache{'sectionList'});
-    my @sectionsSelected = split(':',$cache{'sectionsSelected'});
-    $Ptr .= &Apache::lonhtmlcommon::MultipleSectionSelect(\@sections,
-                                                          \@sectionsSelected,
-                                                          'Statistics');
-    $Ptr .= '</td></tr>'."\n";
-    $Ptr .= &ProblemStatisticsButtons($cache{'DisplayFormat'}, 
-                                      $cache{'DisplayLegend'},
-                                      $cache{'SortProblems'});
-    $Ptr .= '</table>';
-    if($cache{'DisplayLegend'} eq 'Show Legend') {
-        $Ptr .= &ProblemStatisticsLegend();
-    }
-    $r->print($Ptr);
+    &Apache::lonhtmlcommon::Close_PrgWin($r,\%prog_state);
     $r->rflush();
-    untie(%cache);
+}
 
-    my ($result, $orderedProblems) =
-        &InitializeProblemStatistics($cacheDB, $students, $courseID, $c, $r);
-    if($result ne 'OK') {
-        return;
-    }
+###############################################
+###############################################
+
+=pod 
 
-    unless(tie(%cache,'GDBM_File',$cacheDB,&GDBM_READER(),0640)) {
-        $r->print('Unable to tie database.6');
+=item &BuildProblemStatisticsPage()
+
+Main interface to problem statistics.
+
+=cut
+
+###############################################
+###############################################
+sub BuildProblemStatisticsPage {
+    my ($r,$c)=@_;
+    #
+    $output_mode = 'html';
+    $show = 'grouped';
+    #
+    $r->print(&CreateInterface());
+    $r->print('<input type="hidden" name="statsfirstcall" value="no" />');
+    $r->print('<input type="hidden" name="sortby" value="'.$ENV{'form.sortby'}.
+              '" />');
+    if (! exists($ENV{'form.statsfirstcall'})) {
+        $r->print(<<ENDMSG);
+<p>
+<font size="+1">
+Please make your selections in the boxes above and hit 
+the button marked &quot;Update&nbsp;Display&quot;.
+</font>
+</p>
+ENDMSG
         return;
     }
-    &BuildStatisticsTable(\%cache, $cache{'DisplayFormat'}, 
-                          $cache{'SortProblems'}, $orderedProblems, 
-                          \@Header, $r, $color);
-    untie(%cache);
-
+    #
+    &Gather_Student_Data($r);
+    #
+    #
+    if ($output_mode eq 'html') {
+        $r->print("<h2>".
+                  $ENV{'course.'.$ENV{'request.course.id'}.'.description'}.
+                  "</h2>\n");
+        $r->print("<h3>".localtime(time)."</h3>");
+        $r->rflush();
+        if ($show eq 'grouped') {
+            &output_html_grouped_by_sequence($r);
+        } elsif ($show eq 'ungrouped') {
+            &output_html_ungrouped($r);
+        }
+    } elsif ($output_mode eq 'excel') {
+        $r->print("<h2>Preparing Excel Spreadsheet</h2>");
+        &output_excel($r);
+    } elsif ($output_mode eq 'plot') {
+        if ($show eq 'deg of diff') {
+            &plot_statistics($r,'DoDiff');
+        } elsif ($show eq 'per wrong') {
+            &plot_statistics($r,'%Wrng');
+        }
+    } else {
+        $r->print("<h1>Not implemented</h1>");
+    }
     return;
 }
 
-sub BuildGraphicChart {
-    my ($graph,$cacheDB,$courseDescription,$students,$courseID,$r,$c)=@_;
-    my %cache;
-    my $max = 0;
-
-    my ($result, undef) = 
-        &InitializeProblemStatistics($cacheDB, $students, $courseID, $c, $r);
-    if($result ne 'OK') {
-        return;
+###############################################
+###############################################
+
+=pod 
+
+=item &output_html_grouped_by_sequence()
+
+Presents the statistics data as an html table organized by the order
+the assessments appear in the course.
+
+=cut
+
+###############################################
+###############################################
+sub output_html_grouped_by_sequence {
+    my ($r) = @_;
+    my $problem_num = 0;
+    #$r->print(&ProblemStatisticsLegend());
+    my @Header = ("Title","Part","#Stdnts","Tries","Mod",
+                  "Mean","#YES","#yes","%Wrng","DoDiff",
+                  "S.D.","Skew.");#,"D.F.1st","D.F.2nd");
+    # #FFFFE6 #EEFFCC #DDFFFF FFDDDD #DDFFDD #FFDDFF
+    foreach my $sequence (&Apache::lonstatistics::Sequences_with_Assess()) {
+        next if ($sequence->{'num_assess'}<1);
+        $r->print("<h3>".$sequence->{'title'}."</h3>");
+        $r->print('<table border="0"><tr><td bgcolor="#777777">'."\n");
+        $r->print('<table border="0" cellpadding="3">'."\n");
+        $r->print('<tr bgcolor="#FFFFE6"><th>'.
+                  join("</th><th>",@Header)."</th></tr>\n");
+        foreach my $resource (@{$sequence->{'contents'}}) {
+            next if ($resource->{'type'} ne 'assessment');
+            foreach my $part (@{$resource->{'parts'}}) {
+                $problem_num++;
+                my ($num,$tries,$mod,$mean,$Solved,$solved,$DegOfDiff,$STD,
+                    $SKEW) = &get_statistics($resource->{'symb'},$part);
+                #
+                $part = '&nbsp;' if ($part == 0);
+                #
+                my $wrongpercent = 0;
+                if (defined($num) && $num > 0) {
+                    $wrongpercent=int(10*100*($num-$Solved+$solved)/$num)/10;
+                }
+                my $option = '';
+                $r->print('<tr>'.&statistics_html_table_data
+                          ($resource,$part,$num,$tries,$mod,$mean,$Solved,
+                           $solved,$wrongpercent,$DegOfDiff,$STD,$SKEW,
+                           $option).
+                          "</tr>\n");
+            }
+        }
+        $r->print("</table>\n");
+        $r->print("</td></tr></table>\n");
+        $r->rflush();
     }
+    #
+    return;
+}
+
+###############################################
+###############################################
+
+=pod 
+
+=item &output_html_ungrouped()
 
-    unless(tie(%cache,'GDBM_File',$cacheDB,&GDBM_READER(),0640)) {
-        return 'Unable to tie database.7';
+Presents the statistics data in a single html table which can be sorted by
+different columns.
+
+=cut
+
+###############################################
+###############################################
+sub output_html_ungrouped {
+    my ($r,$option) = @_;
+    #
+    my $problem_num = 0;
+    my $show_container = 0;
+    my $show_part = 0;
+    #$r->print(&ProblemStatisticsLegend());
+    my @Header = ("Title","Part","#Stdnts","Tries","Mod",
+                  "Mean","#YES","#yes","%Wrng","DoDiff",
+                  "S.D.","Skew");#,"D.F.1st","D.F.2nd");
+    #
+    my $sortby = undef;
+    foreach (@Header) {
+        if ($ENV{'form.sortby'} eq $_) {
+            $sortby = $_;
+        }
+    }
+    if (! defined($sortby) || $sortby eq '') {
+        $sortby = 'Container';
+    }
+    # If there is more than one sequence, list their titles
+    my @Sequences = &Apache::lonstatistics::Sequences_with_Assess();
+    if (@Sequences > 1) {
+        unshift(@Header,"Container");
+        $show_container = 1;
+    }
+    # 
+    # If the option for showing the problem number is needed, push that
+    # on the list too
+    if (defined($option) && $option =~ /show probnum/) {
+        unshift(@Header,"P#");
     }
-   
-    my @problems = split(':::', $cache{'problemList'});
-    my @values = ();
-    foreach (@problems) {
-        my $data = 0;
-        if($graph eq 'DoDiffGraph') {
-            $data = sprintf("%.2f", $cache{$_.':degreeOfDifficulty'}),
-        } else {
-            $data = sprintf("%.1f", $cache{$_.':percentWrong'}),
+    #
+    $r->print('<table border="0"><tr><td bgcolor="#777777">'."\n");
+    $r->rflush();
+    #
+    # Compile the data
+    my @Statsarray;
+    foreach my $sequence (@Sequences) {
+        next if ($sequence->{'num_assess'}<1);
+        foreach my $resource (@{$sequence->{'contents'}}) {
+            next if ($resource->{'type'} ne 'assessment');
+            foreach my $part (@{$resource->{'parts'}}) {
+                $problem_num++;
+                my ($num,$tries,$mod,$mean,$Solved,$solved,$DegOfDiff,$STD,
+                    $SKEW) = &get_statistics($resource->{'symb'},$part);
+                #
+                $show_part = 1 if ($part ne '0');
+                $part = '&nbsp;' if ($part == 0);
+                #
+                my $wrongpercent = 0;
+                if (defined($num) && $num > 0) {
+                    $wrongpercent=int(10*100*($num-$Solved+$solved)/$num)/10;
+                }
+                push (@Statsarray,
+                      { 'sequence' => $sequence,
+                        'resource' => $resource,
+                        'Title' => $resource->{'title'},
+                        'Part'  => $part,
+                        '#Stdnts' => $num,
+                        'Tries' => $tries,
+                        'Mod' => $mod,
+                        'Mean' => $mean,
+                        '#YES' => $Solved,
+                        '#yes' => $solved,
+                        '%Wrng' => $wrongpercent,
+                        'DoDiff' => $DegOfDiff,
+                        'S.D.' => $STD,
+                        'Skew' => $SKEW,
+                        'problem_num' => $problem_num,
+                      });
+            }
         }
-        if($max < $data) {
-            $max = $data;
+    }
+    #
+    # Table Headers
+    $r->print('<table border="0" cellpadding="3">'."\n");
+    my $Str = '';
+    foreach (@Header) {
+        next if ($_ eq 'Part' && !$show_part);
+        # Do not allow sorting on some fields
+        if ($_ eq $sortby || /^(Part|P\#)$/) {  
+            $Str .= '<th>'.$_.'</th>';
+        } else {
+            $Str .= '<th>'.
+     '<a href="javascript:document.Statistics.sortby.value='."'$_'".
+         ';document.Statistics.submit();">'.
+             $_.'</a></th>';
         }
-        push(@values, $data);
     }
-    untie(%cache);
-
-    my $sendValues = join(',', @values);
-    my $sendCount = scalar(@values);
-
-    my $title = '';
-    if($graph eq 'DoDiffGraph') {
-	$title = 'Degree-of-Difficulty';
+    $r->print('<tr bgcolor="#FFFFE6">'.$Str."</tr>\n");
+    #
+    # Sort the data
+    my @OutputOrder;
+    if ($sortby eq 'Container') {
+        @OutputOrder = @Statsarray;
     } else {
-	$title = 'Wrong-Percentage';
+        # $sortby is already defined, so we can charge ahead
+        if ($sortby =~ /^(title|part)$/i) {
+            # Alpha comparison
+            @OutputOrder = sort {
+                lc($a->{$sortby}) cmp lc($b->{$sortby}) ||
+                    lc($a->{'Title'}) cmp lc($b->{'Title'}) ||
+                        lc($a->{'Part'}) cmp lc($b->{'Part'});
+            } @Statsarray;
+        } else {
+            # Numerical comparison
+            @OutputOrder = 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'});
+                }
+                $retvalue;
+            } @Statsarray;
+        }
     }
-    my @GData = ($courseDescription, 'Problems', $title, $max, $sendCount, 
-                 $sendValues);
-
-    $r->print('</form>'."\n");
-    $r->print('<IMG src="/cgi-bin/graph.gif?'.(join('&', @GData)).
-              '" border="1" />');
-    $r->print('<form>'."\n");
-
+    $option .= ',no part' if (! $show_part);
+    foreach my $row (@OutputOrder) {
+        $r->print('<tr>');
+        if (defined($option) && $option =~ /show probnum/) {
+            $r->print('<td bgcolor="#FFFFE6">'.$row->{'problem_num'}.'</td>');
+        }
+        if ($show_container) {
+            $r->print('<td bgcolor="#FFFFE6">'
+                      .$row->{'sequence'}->{'title'}.'</td>');
+        }
+        $r->print(&statistics_html_table_data
+                  ($row->{'resource'},$row->{'Part'},$row->{'#Stdnts'},
+                   $row->{'Tries'},$row->{'Mod'},$row->{'Mean'},
+                   $row->{'#YES'},$row->{'#yes'},$row->{"\%Wrng"},
+                   $row->{'DoDiff'},$row->{'S.D.'},$row->{'Skew'},
+                   $option));
+        $r->print("</tr>\n");
+    }
+    $r->print("</table>\n");
+    $r->print("</td></tr></table>\n");
+    $r->rflush();
+    #
     return;
 }
 
-#---- Problem Statistics Web Page ---------------------------------------
+###############################################
+###############################################
 
-sub CreateProblemStatisticsTableHeading {
-    my ($headings,$r)=@_;
+=pod 
 
-    my $Str='';
-    $Str .= '<tr>'."\n";
-    $Str .= '<th bgcolor="#ffffe6">P#</th>'."\n";
-    foreach(@$headings) {
-	$Str .= '<th bgcolor="#ffffe6">';
-        $Str .= '<a href="/adm/statistics?reportSelected=';
-        $Str .= &Apache::lonnet::escape('Problem Statistics');
-        $Str .= '&ProblemStatisticsSort=';
-        $Str .= &Apache::lonnet::escape($_).'">'.$_.'</a>&nbsp</th>'."\n";
-    }
-    $Str .= "\n".'</tr>'."\n";    
+=item &output_excel()
 
-    return $Str;
-}
+Presents the statistical data in an Excel 95 compatable spreadsheet file.
 
-sub BuildStatisticsTable {
-    my ($cache,$displayFormat,$sortProblems,$orderedProblems,$headings,
-        $r,$color)=@_;
-
-    my $count = 1;
-    my $currentSequence = -1;
-    foreach(@$orderedProblems) {
-        my ($sequence,$problem,$part)=split(':', $_);
-        if($cache->{'StatisticsMaps'} ne 'All Maps'  &&
-           $cache->{'StatisticsMaps'} ne $cache->{$sequence.':title'}) {
-            next;
-        }
-
-        if($currentSequence == -1 || 
-           ($sortProblems eq 'Sort Within Sequence' && 
-            $currentSequence != $sequence)) {
-            if($displayFormat ne 'Display CSV Format') {
-                if($currentSequence ne -1) {
-                    $r->print('</table>');
-                    $r->print('</td></tr></table><br>');
+=cut
+
+###############################################
+###############################################
+sub output_excel {
+    my ($r) = @_;
+    my $filename = '/prtspool/'.
+        $ENV{'user.name'}.'_'.$ENV{'user.domain'}.'_'.
+            time.'_'.rand(1000000000).'.xls';
+    #
+    my $excel_workbook = undef;
+    my $excel_sheet = undef;
+    #
+    my $rows_output = 0;
+    my $cols_output = 0;
+    #
+    # Create sheet
+    $excel_workbook = Spreadsheet::WriteExcel->new('/home/httpd'.$filename);
+    #
+    # Check for errors
+    if (! defined($excel_workbook)) {
+        $r->log_error("Error creating excel spreadsheet $filename: $!");
+        $r->print("Problems creating new Excel file.  ".
+                  "This error has been logged.  ".
+                  "Please alert your LON-CAPA administrator");
+        return ;
+    }
+    #
+    # The excel spreadsheet stores temporary data in files, then put them
+    # together.  If needed we should be able to disable this (memory only).
+    # The temporary directory must be specified before calling 'addworksheet'.
+    # File::Temp is used to determine the temporary directory.
+    $excel_workbook->set_tempdir($Apache::lonnet::tmpdir);
+    #
+    # Add a worksheet
+    my $sheetname = $ENV{'course.'.$ENV{'request.course.id'}.'.description'};
+    if (length($sheetname) > 31) {
+        $sheetname = substr($sheetname,0,31);
+    }
+    $excel_sheet = $excel_workbook->addworksheet($sheetname);
+    #
+    # Put the course description in the header
+    $excel_sheet->write($rows_output,$cols_output++,
+                   $ENV{'course.'.$ENV{'request.course.id'}.'.description'});
+    $cols_output += 3;
+    #
+    # Put a description of the sections listed
+    my $sectionstring = '';
+    my @Sections = @Apache::lonstatistics::SelectedSections;
+    if (scalar(@Sections) > 1) {
+        if (scalar(@Sections) > 2) {
+            my $last = pop(@Sections);
+            $sectionstring = "Sections ".join(', ',@Sections).', and '.$last;
+        } else {
+            $sectionstring = "Sections ".join(' and ',@Sections);
+        }
+    } else {
+        if ($Sections[0] eq 'all') {
+            $sectionstring = "All sections";
+        } else {
+            $sectionstring = "Section ".$Sections[0];
+        }
+    }
+    $excel_sheet->write($rows_output,$cols_output++,$sectionstring);
+    $cols_output += scalar(@Sections);
+    #
+    # Put the date in there too
+    $excel_sheet->write($rows_output,$cols_output++,
+                        'Compiled on '.localtime(time));
+    #
+    $rows_output++; 
+    $cols_output=0;
+    #
+    # Add the headers
+    my @Header = ("Container","Title","Part","#Stdnts","Tries","Mod",
+                  "Mean","#YES","#yes","%Wrng","DoDiff",
+                  "S.D.","Skew.");#,"D.F.1st","D.F.2nd");
+    foreach (@Header) {
+        $excel_sheet->write($rows_output,$cols_output++,$_);
+    }
+    $rows_output++;
+    #
+    # Write the data
+    foreach my $sequence (&Apache::lonstatistics::Sequences_with_Assess()) {
+        next if ($sequence->{'num_assess'}<1);
+        foreach my $resource (@{$sequence->{'contents'}}) {
+            next if ($resource->{'type'} ne 'assessment');
+            foreach my $part (@{$resource->{'parts'}}) {
+                $cols_output=0;
+                my ($num,$tries,$mod,$mean,$Solved,$solved,$DegOfDiff,$STD,
+                    $SKEW) = &get_statistics($resource->{'symb'},$part);
+                #
+                if (!defined($part) || $part eq '') {
+                    $part = ' ';
                 }
-                if($sortProblems eq 'Sort Within Sequence') {
-                    $r->print('<b>'.$cache->{$sequence.':title'}.'</b>');
+                my $wrongpercent = 0;
+                if (defined($num) && $num > 0) {
+                    $wrongpercent=int(10*100*($num-$Solved+$solved)/$num)/10;
                 }
-                $r->print('<table border="0"><tr><td bgcolor="#777777">'."\n");
-                $r->print('<table border="0" cellpadding="3">'."\n");
-                $r->print(&CreateProblemStatisticsTableHeading($headings, $r));
-            } else {
-                if($sortProblems eq 'Sort Within Sequence') {
-                    $r->print('"'.$cache->{$sequence.':title'}.'"');
+                foreach ($sequence->{'title'},$resource->{'title'},$part,
+                         $num,$tries,$mod,$mean,$Solved,$solved,$wrongpercent,
+                         $DegOfDiff,$STD,$SKEW) {
+                    $excel_sheet->write($rows_output,$cols_output++,$_);
                 }
-                $r->print('<br>');
+                $rows_output++;
             }
-            $currentSequence = $sequence;
         }
-
-        my $ref = '<a href="'.$cache->{$problem.':source'}.
-                  '" target="_blank">'.$cache->{$problem.':title'}.'</a>';
-        my $title = $cache->{$problem.':title'};
-        if($part != 0) {
-            $title .= ' Part '.$part;
-        }
-        my $source = $cache->{$problem.':source'};
-        my $tableData = join('&', $ref, $title, $source,
-                       $cache->{$_.':studentCount'},
-                       $cache->{$_.':totalTries'},
-                       $cache->{$_.':maxTries'},
-                       $cache->{$_.':mean'},
-                       $cache->{$_.':correct'},
-                       $cache->{$_.':correctByOverride'},
-                       $cache->{$_.':percentWrong'},
-                       $cache->{$_.':degreeOfDifficulty'},
-                       $cache->{$_.':standardDeviation'},
-                       $cache->{$_.':skewness'},
-                       $cache->{$_.':discriminationFactor1'},
-                       $cache->{$_.':discriminationFactor2'});
-
-        &TableRow($displayFormat,$tableData,$count,$r,$color);
-
-        $count++;
-    }
-    if($displayFormat ne 'Display CSV Format') {
-        $r->print('</table>'."\n");
-        $r->print('</td></tr></table>');
-    } else {
-        $r->print('<br>');
     }
-
+    #
+    # Write the excel file
+    $excel_workbook->close();
+    # Tell the user where to get their excel file
+    $r->print('<br />'.
+              '<a href="'.$filename.'">Your Excel spreadsheet.</a>'."\n");
+    $r->rflush();
     return;
 }
 
-sub TableRow {
-    my ($displayFormat,$Str,$RealIdx,$r,$color)=@_;
-    my($ref,$title,$source,$StdNo,$TotalTries,$MxTries,$Avg,$YES,$Override,
-       $Wrng,$DoD,$SD,$Sk,$_D1,$_D2)=split(/\&/,$Str);	
-    my $Ptr;
-    if($displayFormat eq 'Display CSV Format') {
-        $Ptr='"'.$RealIdx.'",'."\n".
-             '"'.$title.'",'."\n".
-             '"'.$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".
-             "<br>\n";
+###############################################
+###############################################
 
-        $r->print("\n".$Ptr);
-    } else {
-        $Ptr='<tr>'."\n".
-             '<td bgcolor="#ffffe6">'.$RealIdx.'</td>'."\n".
-             '<td bgcolor="#ffffe6">'.$ref.'</td>'."\n".
-             '<td bgcolor='.$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";
-        $r->print($Ptr.'</tr>'."\n");
-    }
+=pod 
 
-    return;
-}
+=item &statistics_html_table_data()
 
-# 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, $displayLegend, $sortProblems)=@_;
-
-    my $Ptr = '<tr><td></td><td align="left">';
-    $Ptr .= '<input type="submit" name="DoDiffGraph" ';
-    $Ptr .= 'value="Degree of Difficulty" />'."\n";
-    $Ptr .= '</td><td align="left">';
-    $Ptr .= '<input type="submit" name="PercentWrongGraph" ';
-    $Ptr .= 'value="Percent Wrong" />'."\n";
-    $Ptr .= '</td></tr><tr><td></td><td>'."\n";
-    $Ptr .= '<input type="submit" name="SortProblems" ';
-    if($sortProblems eq 'Sort All Problems') {
-        $Ptr .= 'value="Sort Within Sequence" />'."\n";
-    } else {
-        $Ptr .= 'value="Sort All Problems" />'."\n";
-    }
-    $Ptr .= '</td><td align="left">';
-    $Ptr .= '<input type="submit" name="DisplayLegend" ';
-    if($displayLegend eq 'Show Legend') {
-        $Ptr .= 'value="Hide Legend" />'."\n";
-    } else {
-        $Ptr .= 'value="Show Legend" />'."\n";
+Help function used to format the rows for HTML table output.
+
+=cut
+
+###############################################
+###############################################
+sub statistics_html_table_data {
+    my ($resource,$part,$num,$tries,$mod,$mean,$Solved,$solved,$wrongpercent,
+        $DegOfDiff,$STD,$SKEW,$options) = @_;
+    my $row = '';
+    $row .= '<td bgcolor="#FFFFE6">'.
+        '<a href="'.$resource->{'src'}.'" target="_blank" >'.
+            $resource->{'title'}.'</a>'.
+                '</td>';
+    $row .= '<td bgcolor="#FFFFE6">'.$part.'</td>' if ($options !~ /no part/);
+    foreach ($num,$tries) {
+        $row .= '<td bgcolor="#EEFFCC" align="right">'.$_.'</td>';
+    }
+    foreach ($mod) {
+        $row .= '<td bgcolor="#DDFFFF" align="right">'.$_.'</td>';
+    }
+    foreach ($mean) {
+        $row .= '<td bgcolor="#DDFFFF" align="right">'.
+                  sprintf("%5.2f",$_).'</td>';
+    }
+    foreach ($Solved,$solved) {
+        $row .= '<td bgcolor="#DDFFFF" align="right">'.$_.'</td>';
+    }
+    foreach ($wrongpercent) {
+        $row .= '<td bgcolor="#DDFFFF" align="right">'.
+                  sprintf("%5.1f",$_).'</td>';
+    }
+    foreach ($DegOfDiff,$STD,$SKEW) {
+        $row .= '<td bgcolor="#FFDDDD" align="right">'.
+                  sprintf("%5.2f",$_).'</td>';
+    }
+    return $row;
+}
+
+###############################################
+###############################################
+
+=pod 
+
+=item &plot_statistics()
+
+=cut
+
+###############################################
+###############################################
+sub plot_statistics {
+    my ($r,$datafield) = @_;
+    my @Data;
+    #
+    my %Fields = ('#Stdnts'=> 0,
+                  'Tries'  => 1,
+                  'Mod'    => 2,
+                  'Mean'   => 3,
+                  '#YES'   => 4,
+                  '#yes'   => 5,
+                  '%Wrng'  => 9,
+                  'DoDiff' => 6,
+                  'S.D.'   => 7,
+                  'Skew'   => 8,);
+    #
+    my $field = '%Wrng';
+    foreach (keys(%Fields)) {
+        $field = $_ if ($datafield eq $_);
+    }
+    my $fieldindex = $Fields{$field};
+    #
+    my $Max = 0;
+    foreach my $sequence (&Apache::lonstatistics::Sequences_with_Assess()) {
+        next if ($sequence->{'num_assess'}<1);
+        foreach my $resource (@{$sequence->{'contents'}}) {
+            next if ($resource->{'type'} ne 'assessment');
+            foreach my $part (@{$resource->{'parts'}}) {
+                my @Results= &get_statistics($resource->{'symb'},$part);
+                my ($num,$Solved,$solved) = @Results[0,4,5];
+                my $wrongpercent = 0;
+                if (defined($num) && $num > 0) {
+                    $wrongpercent=int(10*100*($num-$Solved+$solved)/$num)/10;
+                }
+                push (@Results,$wrongpercent);
+                my $data = $Results[$fieldindex];
+                $data = 0 if ($data eq 'nan');
+                $Max = $data if ($Max<$data);
+                push (@Data,$data);
+            }
+        }
     }
-    $Ptr .= '</td><td align="left">';
-    $Ptr .= '<input type="submit" name="DisplayCSVFormat" ';
-    if($displayFormat eq 'Display CSV Format') {
-        $Ptr .= 'value="Display Table Format" />'."\n";
-    } else {
-        $Ptr .= 'value="Display CSV Format" />'."\n";
+    #
+    # Print out plot request
+    my $title = 'Percent Wrong';
+    if ($field eq 'DoDiff') {
+        $title = 'Degree of Difficulty';
+    }
+    my $yaxis = 'Percent';
+    if ($field eq 'DoDiff') {
+        $yaxis = '';
+    } elsif ($field ne '%Wrng') {
+        $yaxis = '';
+    }
+    #
+    # Determine appropriate value for $Max
+    if ($field eq 'DoDiff') {
+        if ($Max > 0.5) {
+            $Max = 1;
+        } elsif ($Max > 0.2) {
+            $Max = 0.5;
+        } elsif ($Max > 0.1) {
+            $Max = 0.2;
+        }
+    } elsif ($field eq '%Wrng') {
+        if ($Max > 50) {
+            $Max = 100;
+        } elsif ($Max > 25) {
+            $Max = 50;
+        } elsif ($Max > 20) {
+            $Max = 25;
+        } elsif ($Max > 10) {
+            $Max = 20;
+        } elsif ($Max > 5) {
+            $Max = 10;
+        } else {
+            $Max = 5;
+        }
     }
-    $Ptr .= '</td></tr>';
-
-    return $Ptr;
+    
+    $r->print("<p>".&DrawGraph(\@Data,$title,'Problem Number',$yaxis,
+                               $Max)."</p>\n");
+    #
+    # Print out the data
+    $ENV{'form.sortby'} = 'Contents';
+    &output_html_ungrouped($r,'show probnum');
+    return;
 }
 
+###############################################
+###############################################
+
+=pod 
+
+=item &DrawGraph()
+
+=cut
+
+###############################################
+###############################################
+sub DrawGraph {
+    my ($values,$title,$xaxis,$yaxis,$Max)=@_;
+    $title = '' if (! defined($title));    
+    $xaxis = '' if (! defined($xaxis));
+    $yaxis = '' if (! defined($yaxis));
+    #
+    my $sendValues = join(',', @$values);
+    my $sendCount = scalar(@$values);
+    if ( $Max > 1 ) {
+	if ($Max % 10) {
+            if ( int($Max) < $Max ) {
+	    	$Max++;
+		$Max = int($Max);
+	    }
+	}
+    } else { 
+        $Max = 1; 
+    }
+    my @GData = ($title,$xaxis,$yaxis,$Max,$sendCount,$sendValues);
+    return '<IMG src="/cgi-bin/graph.png?'.
+        (join('&', @GData)).'" border="1" />';
+}
+
+sub get_statistics {
+    my ($symb,$part) = @_;
+    #
+    my $courseid = $ENV{'request.course.id'};
+    #
+    my $students = \@Apache::lonstatistics::Students;
+    if ($Apache::lonstatistics::SelectedSections[0] eq 'all') {
+        $students = undef;
+    }
+    my @Results = &Apache::loncoursedata::get_problem_statistics
+                        ($students,$symb,$part,$courseid);
+    return @Results;
+}
+
+###############################################
+###############################################
+
+=pod 
+
+=item &ProblemStatisticsLegend()
+
+=cut
+
+###############################################
+###############################################
 sub ProblemStatisticsLegend {
     my $Ptr = '';
     $Ptr = '<table border="0">';
@@ -507,8 +906,8 @@ sub ProblemStatisticsLegend {
     $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>[Criterion to group students into %27 Upper Students - ';
+    $Ptr .= 'and %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: ';
@@ -517,291 +916,9 @@ sub ProblemStatisticsLegend {
     $Ptr .= '<tr><td><b>Disc.</b></td>';
     $Ptr .= '<td>Number of Students had at least one discussion.';
     $Ptr .= '</td></tr></table>';
-
     return $Ptr;
 }
 
-sub ExtractStudentData {
-    my ($cache, $students)=@_;
-
-    my @problemList=();
-    my %problemData;
-    foreach my $sequence (split(':', $cache->{'orderedSequences'})) {
-        foreach my $problemID (split(':', $cache->{$sequence.':problems'})) {
-            foreach my $part (split(/\:/,$cache->{$sequence.':'.
-                                                  $problemID.
-                                                  ':parts'})) {
-                my $id = $sequence.':'.$problemID.':'.$part;
-                push(@problemList, $id);
-                my $totalTries = 0;
-                my $totalAwarded = 0;
-                my $correct = 0;
-                my $correctByOverride = 0;
-                my $studentCount = 0;
-                my $maxTries = 0;
-                my $totalFirst = 0;
-                my @studentTries=();
-                foreach(@$students) {
-                    my $code = $cache->{"$_:$problemID:$part:code"};
-
-                    if(defined($cache->{$_.':error'}) || $code eq ' ' ||
-                       $cache->{"$_:$problemID:NoVersion"} eq 'true') {
-                        next;
-                    }
-
-                    $studentCount++;
-                    my $tries =  $cache->{"$_:$problemID:$part:tries"};
-                    if($maxTries < $tries) {
-                        $maxTries = $tries;
-                    }
-                    $totalTries += $tries;
-                    push(@studentTries, $tries);
-
-                    my $awarded = $cache->{"$_:$problemID:$part:awarded"};
-                    $totalAwarded += $awarded;
-
-                    if($code eq '*') {
-                        $correct++;
-                        if($tries == 1) {
-                            $totalFirst++;
-                        }
-                    } elsif($code eq '+') {
-                        $correctByOverride++;
-                    }
-                }
-
-                my $studentTriesJoined = join(':::', @studentTries);
-                $problemData{$id.':sequenceTitle'} = 
-                    $cache->{$sequence.':title'};
-                $problemData{$id.':studentCount'} = $studentCount;
-                $problemData{$id.':totalTries'} = $totalTries;
-                $problemData{$id.':studentTries'} = $studentTriesJoined;
-                $problemData{$id.':totalAwarded'} = $totalAwarded;
-                $problemData{$id.':correct'} = $correct;
-                $problemData{$id.':correctByOverride'} = $correctByOverride;
-                $problemData{$id.':wrong'} = $studentCount - 
-                                             ($correct + $correctByOverride);
-                $problemData{$id.':maxTries'} = $maxTries;
-                $problemData{$id.':totalFirst'} = $totalFirst;
-            }
-        }
-    }
-
-    my @upperStudents1=();
-    my @lowerStudents1=();
-    my @upperStudents2=();
-    my @lowerStudents2=();
-    my $upperCount = int(0.27*scalar(@$students));
-    # Discriminant Factor criterion 1
-    my $sortedStudents = &SortDivideByTries($students,$cache,':totalAwarded');
-
-    for(my $i=0; $i<$upperCount; $i++) {
-        push(@lowerStudents1, $sortedStudents->[$i]);
-        push(@upperStudents1, $sortedStudents->[(scalar(@$students)-$i-1)]);
-    }
-
-    $problemData{'studentsUpperListCriterion1'}=join(':::', @upperStudents1);
-    $problemData{'studentsLowerListCriterion1'}=join(':::', @lowerStudents1);
-
-    # Discriminant Factor criterion 2
-    $sortedStudents = &SortDivideByTries($students, $cache, ':totalSolved');
-
-    for(my $i=0; $i<$upperCount; $i++) {
-        push(@lowerStudents2, $sortedStudents->[$i]);
-        push(@upperStudents2, $sortedStudents->[(scalar(@$students)-$i-1)]);
-    }
-    $problemData{'studentsUpperListCriterion2'}=join(':::', @upperStudents2);
-    $problemData{'studentsLowerListCriterion2'}=join(':::', @lowerStudents2);
-
-    $problemData{'problemList'} = join(':::', @problemList);
-
-    return \%problemData;
-}
-
-sub SortDivideByTries {
-    my ($toSort, $data, $sortOn)=@_;
-    my @orderedData = sort { ($data->{$a.':totalTries'}) ? 
-                             ($data->{$a.$sortOn}/$data->{$a.':totalTries'}):0
-                             <=>
-                             ($data->{$b.':totalTries'}) ? 
-                             ($data->{$b.$sortOn}/$data->{$b.':totalTries'}):0
-                           } @$toSort;
-
-    return \@orderedData;
-}
-
-sub SortProblems {
-    my ($problemData,$sortBy,$sortProblems,$ascend)=@_;
-
-    my @problems = split(':::', $problemData->{'problemList'});
-    if($sortBy eq "Homework Sets Order") {
-        return \@problems;
-    }
-
-    my $data;
-
-    if   ($sortBy eq "#Stdnts") { $data = ':studentCount'; }
-    elsif($sortBy eq "Tries")   { $data = ':totalTries'; }
-    elsif($sortBy eq "Mod")     { $data = ':maxTries'; }
-    elsif($sortBy eq "Mean")    { $data = ':mean'; }
-    elsif($sortBy eq "#YES")    { $data = ':correct'; }
-    elsif($sortBy eq "#yes")    { $data = ':correctByOverride'; }
-    elsif($sortBy eq "%Wrng")   { $data = ':percentWrong'; }
-    elsif($sortBy eq "DoDiff")  { $data = ':degreeOfDifficulty'; }
-    elsif($sortBy eq "S.D.")    { $data = ':standardDeviation'; }
-    elsif($sortBy eq "Skew.")   { $data = ':skewness'; }
-    elsif($sortBy eq "D.F.1st") { $data = ':discriminationFactor1'; }
-    elsif($sortBy eq "D.F.2nd") { $data = ':discriminationFactor2'; }
-    else                        { return \@problems; }
-
-    my %temp;
-    my @sequenceList=();
-    foreach(@problems) {
-        my ($sequence) = split(':', $_);
-
-        my @array=();
-        my $tempArray;
-        if(defined($temp{$sequence})) {
-            $tempArray = $temp{$sequence};
-        } else {
-            push(@sequenceList, $sequence);
-            $tempArray = \@array;
-            $temp{$sequence} = $tempArray;
-        }
-
-        push(@$tempArray, $_);
-    }
-
-    my @orderedProblems;
-    if($sortProblems eq "Sort Within Sequence") {
-        foreach(keys(%temp)) {
-            my $tempArray = $temp{$_};
-            my @tempOrder =
-                sort { $problemData->{$a.$data} <=> $problemData->{$b.$data} }
-            @$tempArray;
-            $temp{$_} = \@tempOrder;
-        }
-        foreach(@sequenceList) {
-            my $tempArray = $temp{$_};
-            @orderedProblems = (@orderedProblems, @$tempArray);
-        }
-    } else {
-        @orderedProblems = 
-            sort { $problemData->{$a.$data} <=> $problemData->{$b.$data} }
-        @problems;
-    }
-
-    if($ascend eq 'Descending') {
-        @orderedProblems = reverse(@orderedProblems);
-    }
-
-    return \@orderedProblems;
-}
-
-sub CalculateStatistics {
-    my ($data, $cache)=@_;
-
-    my @problems = split(':::', $data->{'problemList'});
-    foreach(@problems) {
-        # Mean
-        my $mean = ($data->{$_.':studentCount'}) ? 
-            ($data->{$_.':totalTries'} / $data->{$_.':studentCount'}) : 0;
-        $data->{$_.':mean'} = sprintf("%.2f", $mean);
-
-        # %Wrong
-        my $pw = ($data->{$_.':studentCount'}) ?
-            (($data->{$_.':wrong'} / $data->{$_.':studentCount'}) * 100.0) : 
-            100.0;
-        $data->{$_.':percentWrong'} = sprintf("%.1f", $pw);
-
-        # Degree of Difficulty
-        my $dod = ($data->{$_.':totalTries'}) ?
-            (1 - (($data->{$_.':correct'} + $data->{$_.':correctByOverride'}) /
-                  $data->{$_.':totalTries'})) : 0;
-
-        $data->{$_.':degreeOfDifficulty'} = sprintf("%.2f", $dod);
-
-        # Factor in mean
-        my @studentTries = split(':::', $data->{$_.':studentTries'});
-        foreach(my $index=0; $index < scalar(@studentTries); $index++) {
-            $studentTries[$index] -= $mean;
-        }
-        my $sumSquared = 0;
-        my $sumCubed = 0;
-        foreach(@studentTries) {
-            my $squared = ($_ * $_);
-            my $cubed = ($squared * $_);
-            $sumSquared += $squared;
-            $sumCubed += $cubed;
-        }
-
-        # Standard deviation
-        my $standardDeviation;
-        if($data->{$_.':studentCount'} - 1 > 0) {
-            $standardDeviation = (sqrt($sumSquared)) / 
-                                 ($data->{$_.':studentCount'} - 1);
-        } else {
-            $standardDeviation =  0.0;
-        }
-        $data->{$_.':standardDeviation'} = sprintf("%.1f", $standardDeviation);
-
-        # Skewness
-        my $skew;
-        if($standardDeviation > 0.0999 && $data->{$_.':studentCount'} > 0) {
-            $skew = (((sqrt($sumSquared)) / $data->{$_.':studentCount'}) / 
-                     ($standardDeviation * 
-                      $standardDeviation * 
-                      $standardDeviation));
-        } else {
-            $skew = 0.0;
-        }
-
-        $data->{$_.':skewness'} = sprintf("%.1f", $skew);
-
-        # Discrimination Factor 1
-        my ($sequence, $problem, $part) = split(':', $_);
-
-        my @upper1 = split(':::', $data->{'studentsUpperListCriterion1'});
-        my @lower1 = split(':::', $data->{'studentsLowerListCriterion1'});
-
-        my $upper1Sum=0;
-        foreach my $name (@upper1) {
-            $upper1Sum += $cache->{"$name:$problem:$part:awarded"};
-        }
-        $upper1Sum = (scalar(@upper1)) ? ($upper1Sum/(scalar(@upper1))) : 0;
-
-        my $lower1Sum=0;
-        foreach my $name (@lower1) {
-            $lower1Sum += $cache->{"$name:$problem:$part:awarded"};
-        }
-        $lower1Sum = (scalar(@lower1)) ? ($lower1Sum/(scalar(@lower1))) : 0;
-
-        my $df1 = $upper1Sum - $lower1Sum;
-        $data->{$_.':discriminationFactor1'} = sprintf("%.2f", $df1);
-
-        # Discrimination Factor 2
-        my @upper2 = split(':::', $data->{'studentsUpperListCriterion2'});
-        my @lower2 = split(':::', $data->{'studentsLowerListCriterion2'});
-
-        my $upper2Sum=0;
-        foreach my $name (@upper2) {
-            $upper2Sum += $cache->{"$name:$problem:$part:awarded"};
-        }
-        $upper2Sum = (scalar(@upper2)) ? ($upper2Sum/(scalar(@upper2))) : 0;
-
-        my $lower2Sum=0;
-        foreach my $name (@lower2) {
-            $lower2Sum += $cache->{"$name:$problem:$part:awarded"};
-        }
-        $lower2Sum = (scalar(@lower2)) ? ($lower2Sum/(scalar(@lower2))) : 0;
-
-        my $df2 = $upper2Sum - $lower2Sum;
-        $data->{$_.':discriminationFactor2'} = sprintf("%.2f", $df2);
-    }
-
-    return;
-}
-
 #---- END Problem Statistics Web Page ----------------------------------------
 
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