--- loncom/interface/statistics/lonproblemstatistics.pm	2004/08/04 15:07:42	1.93
+++ loncom/interface/statistics/lonproblemstatistics.pm	2014/03/03 20:45:05	1.122.2.3
@@ -1,6 +1,6 @@
 # The LearningOnline Network with CAPA
 #
-# $Id: lonproblemstatistics.pm,v 1.93 2004/08/04 15:07:42 matthew Exp $
+# $Id: lonproblemstatistics.pm,v 1.122.2.3 2014/03/03 20:45:05 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -50,7 +50,7 @@ Excel files, and plots.
 package Apache::lonproblemstatistics;
 
 use strict;
-use Apache::lonnet();
+use Apache::lonnet;
 use Apache::loncommon();
 use Apache::lonhtmlcommon;
 use Apache::loncoursedata;
@@ -60,6 +60,8 @@ 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
@@ -71,6 +73,14 @@ my %SeqStat;    # keys are symbs, values
 ## header for plots created with Graph.pm, both of which more than likely do
 ## not support localization.
 ##
+## Additional Notes:
+## Localization can be done and is done before passing the phrases
+## to the output.
+## This might conflict with special characters, e.g. German Umlaute or
+## chinese characters. Do not use such characters in this case.
+## If this failed, consider that the sequence and folder names
+## are also passed to the output and would fail the same way.
+##
 #
 #
 ##
@@ -82,7 +92,7 @@ my %SeqStat;    # keys are symbs, values
 ## 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
+##                                      output.  Passed through &mt().
 ## align           no    (left|right|center)  HTML cell contents alignment
 ## color           yes      html color  HTML cell background color
 ##                                      used to visually group statistics
@@ -121,11 +131,11 @@ my @Fields = (
              align  => 'left',
              color  => '#FFFFE6',
              special  => 'link',
-             sortable => 'yes', 
+             sortable => 'yes',
              selectable => 'no',
              defaultselected => 'yes',
            },
-           { name   => 'part', 
+           { name   => 'part',
              title  => 'Part',
              align  => 'left',
              color  => '#FFFFE6',
@@ -172,7 +182,7 @@ my @Fields = (
              format => '%d',
              sortable  => 'yes',
              graphable => 'yes',
-             long_title => 'Minumum Number of Tries',
+             long_title => 'Minimum Number of Tries',
              selectable => 'yes',
              defaultselected => 'yes',
            },
@@ -231,6 +241,17 @@ my @Fields = (
              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',
@@ -261,7 +282,7 @@ my @Fields = (
              sortable  => 'yes',
              graphable => 'yes',
              long_title => 'Degree of Difficulty'.
-                           '[ 1 - ((#YES+#yes) / Tries) ]',
+                           ' ~[ 1 - ((#YES+#yes) / Tries) ~]',
              selectable => 'yes',
              defaultselected => 'yes',
            },
@@ -320,6 +341,40 @@ my @Fields = (
 #             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 = (
@@ -328,7 +383,7 @@ my @SeqFields = (
              align  => 'left',
              color  => '#FFFFE6',
              special  => 'no',
-             sortable => 'no', 
+             sortable => 'no',
              selectable => 'yes',
              defaultselected => 'no',
            },
@@ -383,7 +438,7 @@ my @SeqFields = (
              format => '%4.2f',
              sortable  => 'no',
              graphable => 'no',
-             long_title => 'Minumum Sequence Score',
+             long_title => 'Minimum Sequence Score',
              selectable => 'yes',
              defaultselected => 'no',
            },
@@ -438,7 +493,7 @@ my @SeqFields = (
              format => '%4.2f',
              sortable  => 'no',
              graphable => 'no',
-             long_title => 'Minumum Number of Correct Problems',
+             long_title => 'Minimum Number of Correct Problems',
              selectable => 'yes',
              defaultselected => 'no',
            },
@@ -463,7 +518,7 @@ my @SeqFields = (
              long_title => 'KR-21 reliability statistic',
              selectable => 'yes',
              defaultselected => 'no',
-           },           
+           },
 );
 
 my %SelectedFields;
@@ -471,35 +526,35 @@ my %SelectedFields;
 sub parse_field_selection {
     #
     # Pull out the defaults
-    if (! defined($ENV{'form.fieldselections'})) {
-        $ENV{'form.fieldselections'} = [];
+    if (! defined($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'}},$field->{'name'});
+                push(@{$env{'form.fieldselections'}},$field->{'name'});
             }
         }
     }
     #
     # Make sure the data we are plotting is there
     my %NeededFields;
-    if (exists($ENV{'form.plot'}) && $ENV{'form.plot'} ne '' &&
-        $ENV{'form.plot'} ne 'none') {
-        if ($ENV{'form.plot'} eq 'degrees') {
+    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') {
+        } elsif ($env{'form.plot'} eq 'tries statistics') {
             $NeededFields{'mean_tries'}++;
             $NeededFields{'std_tries'}++;
             $NeededFields{'problem_num'}++;
         } else {
-            $NeededFields{$ENV{'form.plot'}}++;
+            $NeededFields{$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'}];
+    if (ref($env{'form.fieldselections'}) ne 'ARRAY') {
+        $env{'form.fieldselections'} = [$env{'form.fieldselections'}];
     }
     #
     # Set the field data and the selected fields (for easier checking)
@@ -514,7 +569,7 @@ sub parse_field_selection {
             $field->{'selected'} = 'yes';
             $SelectedFields{$field->{'name'}}++;
         }
-        foreach my $selection (@{$ENV{'form.fieldselections'}}) {
+        foreach my $selection (@{$env{'form.fieldselections'}}) {
             if ($selection eq $field->{'name'} || $selection eq 'all') {
                 $field->{'selected'} = 'yes';
                 $SelectedFields{$field->{'name'}}++;
@@ -530,15 +585,15 @@ sub parse_field_selection {
 }
 
 sub field_selection_input {
-    my $Str = '<select name="fieldselections" multiple size="5">'."\n";
-    $Str .= '<option value="all">all</option>'."\n";
+    my $Str = '<select name="fieldselections" multiple="multiple" size="5">'."\n";
+    $Str .= '<option value="all">'.&mt('all').'</option>'."\n";
     foreach my $field (@Fields) {
         next if ($field->{'selectable'} ne 'yes');
-        $Str .= '    <option value="'.$field->{'name'}.'" ';
+        $Str .= '    <option value="'.$field->{'name'}.'"';
         if ($field->{'selected'} eq 'yes') {
-            $Str .= 'selected ';
+            $Str .= ' selected="selected"';
         }
-        $Str .= '>'.$field->{'title'}.'</option>'."\n";
+        $Str .= '>'.&mt($field->{'title'}).'</option>'."\n";
     }
     $Str .= "</select>\n";
 }
@@ -563,48 +618,41 @@ sub CreateInterface {
     &parse_field_selection();
     #
     my $Str = '';
-    $Str .= &Apache::lonhtmlcommon::breadcrumbs
-        (undef,'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('Enrollment 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 .= &Apache::loncommon::start_data_table();
+    $Str .= &Apache::loncommon::start_data_table_header_row();
+    $Str .= '<th>'.&mt('Sections').'</th>';
+    $Str .= '<th>'.&mt('Groups').'</th>';
+    $Str .= '<th>'.&mt('Access Status').'</th>';
+    $Str .= '<th>'.&mt('Sequences and Folders').'</th>';
+    $Str .= '<th>'.&mt('Statistics').'</th>';
+    $Str .= '<th>'.&mt('Plot Graph').'</th>';
+    $Str .= '<th>'.&mt('Time Period').'</th>';
+    $Str .= &Apache::loncommon::end_data_table_header_row();
     #
-    $Str .= '<tr><td align="center">'."\n";
+    $Str .= &Apache::loncommon::start_data_table_row();
+    $Str .= '<td align="center" valign="top">'."\n";
     $Str .= &Apache::lonstatistics::SectionSelect('Section','multiple',5);
-    $Str .= '</td><td align="center">';
+    $Str .= '</td><td align="center" valign="top">';
+    $Str .= &Apache::lonstatistics::GroupSelect('Group','multiple',5);
+    $Str .= '</td><td align="center" valign="top">';
     $Str .= &Apache::lonhtmlcommon::StatusOptions(undef,undef,5);
-    $Str .= '</td><td align="center">';
+    $Str .= '</td><td align="center" valign="top">';
     #
-    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>'.&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 .= &Apache::lonstatistics::map_select('Maps','multiple,all',5);
+    $Str .= '</td><td align="center" valign="top">';
+    $Str .= &field_selection_input();
+    $Str .= '</td><td align="center" valign="top">';
+    $Str .= &plot_dropdown();
+    $Str .= "\n";
+    $Str .= '</td><td align="center" valign="top">';
+    $Str .= &Apache::lonstathelpers::limit_by_time_form();
+    $Str .= '</td>'."\n";
+    $Str .=  &Apache::loncommon::end_data_table_row();
+    $Str .= &Apache::loncommon::end_data_table();
     #
     $Str .= '<input type="submit" name="GenerateStatistics" value="'.
         &mt('Generate Statistics').'" />';
-    $Str .= '&nbsp;'x5;
-    $Str .= 'Plot '.&plot_dropdown().('&nbsp;'x10);
+    $Str .= ('&nbsp;'x10);
     #
     return $Str;
 }
@@ -622,12 +670,23 @@ Main interface to problem statistics.
 
 ###############################################
 ###############################################
+my $navmap;
+my @sequences;
+
+sub clean_up {
+    undef($navmap);
+    undef(@sequences);
+}
+
 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');
@@ -643,12 +702,15 @@ sub BuildProblemStatisticsPage {
     undef(%SeqStat);
     #
     # Finally let the user know we are here
+    $r->print(&Apache::lonhtmlcommon::breadcrumbs('Overall Problem Statistics',
+                                                'Statistics_Overall_Key'));
+
     my $interface = &CreateInterface($r);
     $r->print($interface);
-    $r->print('<input type="hidden" name="sortby" value="'.$ENV{'form.sortby'}.
+    $r->print('<input type="hidden" name="sortby" value="'.$env{'form.sortby'}.
               '" />');
     #
-    my @CacheButtonHTML = 
+    my @CacheButtonHTML =
         &Apache::lonstathelpers::manage_caches($r,'Statistics','stats_status');
     my $Str;
     foreach my $html (@CacheButtonHTML) {
@@ -656,14 +718,16 @@ sub BuildProblemStatisticsPage {
     }
     #
     $r->print($Str);
-    if (! exists($ENV{'form.firstrun'})) {
-        $r->print('<h3>'.
+    if (! exists($env{'form.firstrun'})) {
+        $r->print('<p class="LC_info"><b>'.
                   &mt('Press "Generate Statistics" when you are ready.').
-                  '</h3><p>'.
+                  '</b></p>'.
+                  '<p class="LC_info">'.
                   &mt('It may take some time to update the student data '.
-                      'for the first analysis.  Future analysis this session '.
-                      ' will not have this delay.').
+                      'for the first analysis. Future analysis this session '.
+                      'will not have this delay.').
                   '</p>');
+	&clean_up();
         return;
     }
     $r->rflush();
@@ -672,29 +736,45 @@ sub BuildProblemStatisticsPage {
     # it does not slow things down noticably.
     &Apache::loncoursedata::populate_weight_table();
     #
-    if (exists($ENV{'form.Excel'})) {
+    ($navmap,@sequences) =
+        &Apache::lonstatistics::selected_sequences_with_assessments();
+    if (! ref($navmap)) {
+        $r->print('<div class="LC_error">'.&mt('A course-wide error occurred.').'</div>'.
+                  '<h3>'.$navmap.'</h3>');
+	&clean_up();
+        return;
+    }
+    if (exists($env{'form.Excel'})) {
+        $r->print('<p>'.
+                  &Apache::lonstatistics::section_and_enrollment_description().
+                  '</p>');
         &Excel_output($r);
-    } else { 
+    } else {
         $r->print('<input type="submit" name="Excel" value="'.
                   &mt('Produce Excel Output').'" />'.'&nbsp;'x5);
         $r->rflush();
+        $r->print('<p>'.
+                  &Apache::lonstatistics::section_and_enrollment_description().
+                  '</p>');
         my $count = 0;
-        foreach my $seq (&Apache::lonstatistics::Sequences_with_Assess()) {
-            $count += $seq->{'num_assess_parts'};
+        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>');
+            $r->print('<p>'.
+                      &mt('Compiling statistics for [quant,_1,problem]',$count).
+                      '</p>');
             if ($count > 30) {
-                $r->print('<h3>'.&mt('This will take some time.').'</h3>');
+                $r->print('<p class="LC_info">'.&mt('This will take some time.').'</p>');
             }
             $r->rflush();
         }
         #
-        my $sortby = $ENV{'form.sortby'};
+        my $sortby = $env{'form.sortby'};
         $sortby = 'container' if (! defined($sortby) || $sortby =~ /^\s*$/);
-        my $plot = $ENV{'form.plot'};
+        my $plot = $env{'form.plot'};
         if ($plot eq '' || $plot eq 'none') {
             undef($plot);
         }
@@ -709,6 +789,7 @@ sub BuildProblemStatisticsPage {
             &output_sequence_statistics($r);
         }
     }
+    &clean_up();
     return;
 }
 
@@ -718,18 +799,14 @@ sub output_sequence_statistics {
     $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(&Apache::loncommon::start_data_table());
     $r->print(&sequence_html_header());
-    foreach my $seq (&Apache::lonstatistics::Sequences_with_Assess()) {
+    foreach my $seq (@sequences) {
         last if ($c->aborted);
-        next if ($seq->{'num_assess'} < 1);
         &compute_sequence_statistics($seq);
         $r->print(&sequence_html_output($seq));
     }
-    $r->print('</table>');
-    $r->print('</table>');
+    $r->print(&Apache::loncommon::end_data_table());
     $r->rflush();
     return;
 }
@@ -745,23 +822,22 @@ sub output_sequence_statistics {
 sub output_html_by_sequence {
     my ($r) = @_;
     my $c = $r->connection();
-    $r->print(&html_preamble());
+    $r->print('<br />'.&html_preamble());
     #
-    foreach my $seq (&Apache::lonstatistics::Sequences_with_Assess()) {
+    foreach my $seq (@sequences) {
         last if ($c->aborted);
-        next if ($seq->{'num_assess'} < 1);
-        $r->print("<h3>".$seq->{'title'}."</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");
+        $r->print("<h3>".$seq->compTitle."</h3>".
+                    &Apache::loncommon::start_data_table().
+                    &Apache::loncommon::start_data_table_header_row().
+                    &statistics_table_header('no container').
+                    &Apache::loncommon::end_data_table_header_row()."\n");
         my @Data = &compute_statistics_on_sequence($seq);
         foreach my $data (@Data) {
-            $r->print('<tr>'.&statistics_html_table_data($data,
-                                                         'no container').
-                      "</tr>\n");
+            $r->print(&Apache::loncommon::start_data_table_row().
+                    &statistics_html_table_data($data,'no container').
+                    &Apache::loncommon::end_data_table_row()."\n");
         }
-        $r->print('</table>'."\n".'</table>'."\n");
+        $r->print(&Apache::loncommon::end_data_table()."\n");
         $r->rflush();
     }
     return;
@@ -771,29 +847,29 @@ sub output_html_stats {
     my ($r)=@_;
     &compute_all_statistics($r);
     $r->print(&html_preamble());
-    &sort_data($ENV{'form.sortby'});
+    &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(&Apache::loncommon::end_data_table());
+            $r->print(&Apache::loncommon::start_data_table().
+                    &Apache::loncommon::start_data_table_row().
+                    &statistics_table_header().
+                    &Apache::loncommon::end_data_table_row());
+        }
+        $r->print(&Apache::loncommon::start_data_table_row().
+                &statistics_html_table_data($data).
+                &Apache::loncommon::end_data_table_row());
     }
-    $r->print("</table>\n</table>\n");
+    $r->print(&Apache::loncommon::end_data_table_row());
     return;
 }
 
 sub html_preamble {
     my $Str='';
     $Str .= "<h2>".
-        $ENV{'course.'.$ENV{'request.course.id'}.'.description'}.
+        $env{'course.'.$env{'request.course.id'}.'.description'}.
         "</h2>\n";
     my ($starttime,$endtime) = &Apache::lonstathelpers::get_time_limits();
     if (defined($starttime) || defined($endtime)) {
@@ -803,8 +879,8 @@ sub html_preamble {
                            &Apache::lonlocal::locallocaltime($endtime)
                            ).'</h3>';
     }
-    $Str .= "<h3>".&mt('Compiled on [_1]',
-                       &Apache::lonlocal::locallocaltime(time))."</h3>";
+    $Str .= "<p>".&mt('Compiled on [_1]',
+                       &Apache::lonlocal::locallocaltime(time))."</p>";
     return $Str;
 }
 
@@ -822,7 +898,7 @@ sub statistics_html_table_data {
     foreach my $field (@Fields) {
         next if ($options =~ /no $field->{'name'}/);
         next if ($field->{'selected'} ne 'yes');
-        $row .= '<td bgcolor="'.$field->{'color'}.'"';
+        $row .= '<td style="background-color:'.$field->{'color'}.'"';
         if (exists($field->{'align'})) {
             $row .= ' align="'.$field->{'align'}.'"';
             }
@@ -850,14 +926,16 @@ sub statistics_table_header {
         next if ($options =~ /no $field->{'name'}/);
         next if ($field->{'selected'} ne 'yes');
         $header_row .= '<th>';
+        my $header_row_text = &mt($field->{'title'});
         if (exists($field->{'sortable'}) && $field->{'sortable'} eq 'yes') {
-            $header_row .= '<a href="javascript:'.
+            $header_row .=
+                '<a href="javascript:'.
                 'document.Statistics.sortby.value='."'".$field->{'name'}."'".
-                    ';document.Statistics.submit();">';
-        }
-        $header_row .= &mt($field->{'title'});
-        if ($options =~ /sortable/) {
-            $header_row.= '</a>';
+                ';document.Statistics.submit();">'.
+                $header_row_text.
+                '</a>';
+        } else {
+            $header_row .= $header_row_text;
         }
         if ($options !~ /no plots/        && 
             exists($field->{'graphable'}) && 
@@ -874,21 +952,21 @@ sub statistics_table_header {
 }
 
 sub sequence_html_header {
-    my $Str .= '<tr>';
+    my $Str .= &Apache::loncommon::start_data_table_header_row();
     foreach my $field (@SeqFields) {
 #        next if ($field->{'selected'} ne 'yes');
         $Str .= '<th bgcolor="'.$field->{'color'}.'"';
-        $Str .= '>'.$field->{'title'}.'</th>';
+        $Str .= '>'.&mt($field->{'title'}).'</th>';
     }
-    $Str .= '</tr>';
+    $Str .= &Apache::loncommon::end_data_table_header_row();
     return $Str;
 }
 
 
 sub sequence_html_output {
     my ($seq) = @_;
-    my $data = $SeqStat{$seq->{'symb'}};
-    my $row = '<tr>';
+    my $data = $SeqStat{$seq->symb};
+    my $row = &Apache::loncommon::start_data_table_row();
     foreach my $field (@SeqFields) {
         next if ($field->{'selected'} ne 'yes');
         $row .= '<td bgcolor="'.$field->{'color'}.'"';
@@ -903,7 +981,7 @@ sub sequence_html_output {
         }
         $row .= '</td>';
     }
-    $row .= '</tr>'."\n";
+    $row .= &Apache::loncommon::end_data_table_row()."\n";
     return $row;
 }
 
@@ -917,7 +995,7 @@ sub sequence_html_output {
 sub make_plot {
     my ($r,$plot) = @_;
     &compute_all_statistics($r);
-    &sort_data($ENV{'form.sortby'});
+    &sort_data($env{'form.sortby'});
     if ($plot eq 'degrees') {
         &degrees_plot($r);
     } elsif ($plot eq 'tries statistics') {
@@ -934,20 +1012,20 @@ sub make_single_stat_plot {
     my $title; my $yaxis;
     foreach my $field (@Fields) {
         next if ($field->{'name'} ne $datafield);
-        $title = $field->{'long_title'};
-        $yaxis = $field->{'title'};
+        $title = &mt($field->{'long_title'});
+        $yaxis = &mt($field->{'title'});
         last;
     }
     if ($title eq '' || $yaxis eq '') {
         # datafield is something we do not know enough about to plot
-        $r->print('<h3>'.
+        $r->print('<p class="LC_warning">'.
                   &mt('Unable to plot the requested statistic.').
-                  '</h3>');
+                  '</p>');
         return;
     }
     #
     # Build up the data sets to plot
-    my @Labels; 
+    my @Labels;
     my @Data;
     my $max = 1;
     foreach my $data (@StatsArray) {
@@ -969,7 +1047,7 @@ sub make_single_stat_plot {
     }
     #
     $r->print("<p>".&Apache::loncommon::DrawBarGraph($title,
-                                                     'Problem Number',
+                                                     &mt('Problem Number'),
                                                      $yaxis,
                                                      $max,
                                                      undef, # colors
@@ -987,7 +1065,7 @@ sub degrees_plot {
     my $plot = '';
     my $ymax = 0;
     my $ymin = 0;
-    my @Disc; my @Diff; my @Labels;    
+    my @Disc; my @Diff; my @Labels;
     foreach my $data (@StatsArray) {
         push(@Labels,$data->{'problem_num'});
         my $disc = $data->{'deg_of_disc'};
@@ -1034,10 +1112,14 @@ sub degrees_plot {
     my $diffdata .= '<data>'.join(',',@Labels).'</data>'.$/.
                     '<data>'.join(',',@Diff).'</data>'.$/;
     #
-    my $title = 'Degree of Discrimination\nand Degree of Difficulty';
+    my $title = &mt('Degree of Discrimination[_1]and Degree of Difficulty','\n');
     if ($xmax > 50) {
-        $title = 'Degree of Discrimination and Degree of Difficulty';
+        $title = &mt('Degree of Discrimination and Degree of Difficulty');
     }
+    my %lt = &Apache::lonlocal::texthash(
+        'alttag' => 'Degree of Discrimination and Degree of Difficulty Plot',
+        'xlabel' => 'Problem Number',
+    );
     #
     $plot=<<"END";
 <gnuplot 
@@ -1049,7 +1131,7 @@ sub degrees_plot {
     align="center"
     border="on"
     transparent="on"
-    alttag="Degree of Discrimination and Degree of Difficulty Plot"
+    alttag="$lt{'alttag'}"
     samples="100"
     bgcolor="xffffff"
     height="$height"
@@ -1060,7 +1142,7 @@ sub degrees_plot {
         box="off" />
     <title>$title</title>
     <axis xmin="0" ymin="$ymin" xmax="$xmax" ymax="$ymax" color="x000000" />
-    <xlabel>Problem Number</xlabel>
+    <xlabel>$lt{'xlabel'}</xlabel>
     <curve 
         linestyle="linespoints" 
         name="DoDisc" 
@@ -1077,7 +1159,7 @@ sub degrees_plot {
     </curve>
 </gnuplot>
 END
-    my $plotresult = 
+    my $plotresult =
         '<p>'.&Apache::lonxml::xmlparse($r,'web',$plot).'</p>'.$/;
     $r->print($plotresult);
     return;
@@ -1122,11 +1204,16 @@ sub tries_data_plot {
                           '<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';
+    my $title = &mt('Mean and S.D. of Tries');
+    if ($xmax > 30) {
+        $title = &mt('Mean and Standard Deviation of Tries');
     }
     #
+    my %lt = &Apache::lonlocal::texthash(
+        'alttag' => 'Mean and S.D of Tries Plot',
+        'xlabel' => 'Problem Number',
+        'ylabel' => 'Number of Tries',
+    );
     $plot=<<"END";
 <gnuplot 
     texfont="10"
@@ -1137,15 +1224,15 @@ sub tries_data_plot {
     align="center"
     border="on"
     transparent="on"
-    alttag="Mean and S.D of Tries Plot"
+    alttag="$lt{'alttag'}"
     samples="100"
     bgcolor="xffffff"
     height="$height"
     width="$width">
     <title>$title</title>
     <axis xmin="0" ymin="0" xmax="$xmax" ymax="$ymax" color="x000000" />
-    <xlabel>Problem Number</xlabel>
-    <ylabel>Number of Tries</ylabel>
+    <xlabel>$lt{'xlabel'}</xlabel>
+    <ylabel>$lt{'ylabel'}</ylabel>
     <curve 
         linestyle="yerrorbars"
         name="S.D. Tries" 
@@ -1162,7 +1249,7 @@ sub tries_data_plot {
     </curve>
 </gnuplot>
 END
-    my $plotresult = 
+    my $plotresult =
         '<p>'.&Apache::lonxml::xmlparse($r,'web',$plot).'</p>'.$/;
     $r->print($plotresult);
     return;
@@ -1170,9 +1257,10 @@ END
 
 sub plot_dropdown {
     my $current = '';
+    my $title;
     #
-    if (defined($ENV{'form.plot'})) {
-        $current = $ENV{'form.plot'};
+    if (defined($env{'form.plot'})) {
+        $current = $env{'form.plot'};
     }
     #
     my @Additional_Plots = (
@@ -1185,7 +1273,7 @@ sub plot_dropdown {
     #
     my $Str= "\n".'<select name="plot" size="1">';
     $Str .= '<option name="none"></option>'."\n";
-    $Str .= '<option name="none2">none</option>'."\n";
+    $Str .= '<option name="none2">'.&mt('none').'</option>'."\n";
     foreach my $field (@Additional_Plots,@Fields) {
         if (! exists($field->{'graphable'}) ||
             $field->{'graphable'} ne 'yes') {
@@ -1193,9 +1281,11 @@ sub plot_dropdown {
         }
         $Str .= '<option value="'.$field->{'name'}.'"';
         if ($field->{'name'} eq $current) {
-            $Str .= ' selected ';
+            $Str .= ' selected="selected"';
         }
-        $Str.= '>'.&mt($field->{'title'}).'</option>'."\n";
+        $title = &mt($field->{'long_title'});
+        $title = &mt($field->{'title'}) if (!$title);
+        $Str.= '>'.$title.'</option>'."\n";
     }
     $Str .= '</select>'."\n";
     return $Str;
@@ -1216,40 +1306,21 @@ sub Excel_output {
     &compute_all_statistics($r);
     my $c = $r->connection;
     return if ($c->aborted());
+    #
+    my ($starttime,$endtime) = &Apache::lonstathelpers::get_time_limits();
     ##
     ## Create the excel workbook
-    my $filename = '/prtspool/'.
-        $ENV{'user.name'}.'_'.$ENV{'user.domain'}.'_'.
-        time.'_'.rand(1000000000).'.xls';
-    my ($starttime,$endtime) = &Apache::lonstathelpers::get_time_limits();
-    #
-    # Create sheet
-    my $excel_workbook = Spreadsheet::WriteExcel->new('/home/httpd'.$filename);
-    #
-    # Check for errors
-    if (! defined($excel_workbook)) {
-        $r->log_error("Error creating excel spreadsheet $filename: $!");
-        $r->print(&mt("Problems creating new Excel file.  ".
-                  "This error has been logged.  ".
-                  "Please alert your LON-CAPA administrator."));
-        return 0;
-    }
-    #
-    # 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);
+    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'};
+    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));
-    #
-    my $format = &Apache::loncommon::define_excel_formats($excel_workbook);
     ##
     ## Begin creating excel sheet
     ##
@@ -1257,31 +1328,32 @@ sub Excel_output {
     #
     # Put the course description in the header
     $excel_sheet->write($rows_output,$cols_output++,
-                   $ENV{'course.'.$ENV{'request.course.id'}.'.description'},
+                   $env{'course.'.$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::lonstathelpers::sections_description
-                            (@Apache::lonstatistics::SelectedSections),
+                        &Apache::lonstatistics::section_and_enrollment_description('plaintext'),
                         $format->{'h3'});
-    $cols_output += scalar(@Apache::lonstatistics::SelectedSections);
+    $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);
+            $time_string .=  &mt('Data collected from [_1] to [_2]',
+                                 &Apache::lonlocal::locallocaltime($starttime),
+                                 &Apache::lonlocal::locallocaltime($endtime));
+        } else {
+            $time_string .=  &mt('Data collected from [_1]',
+                                 &Apache::lonlocal::locallocaltime($starttime));
         }
-        $time_string .= '.';
     } elsif (defined($endtime)) {
-        # See note above about lonlocal:locallocaltime
-        $time_string .= 'Data collected before '.localtime($endtime).'.';
+        $time_string .=  &mt('Data collected before [_1]',
+                             &Apache::lonlocal::locallocaltime($endtime));
     }
     if (defined($time_string)) {
         $excel_sheet->write($rows_output,$cols_output++,$time_string);
@@ -1290,18 +1362,17 @@ sub Excel_output {
     #
     # Put the date in there too
     $excel_sheet->write($rows_output,$cols_output++,
-                        'Compiled on '.localtime(time));
+                        &mt('Compiled on [_1]',&Apache::lonlocal::locallocaltime(time)));
     #
-    $rows_output++; 
+    $rows_output++;
     $cols_output=0;
     ##
     ## Sequence Statistics
-    ## 
+    ##
     &write_headers($excel_sheet,$format,\$rows_output,\$cols_output,
                    \@SeqFields);
-    foreach my $seq (&Apache::lonstatistics::Sequences_with_Assess()) {
-        next if ($seq->{'num_assess'} < 1);
-        my $data = $SeqStat{$seq->{'symb'}};
+    foreach my $seq (@sequences) {
+        my $data = $SeqStat{$seq->symb};
         $cols_output=0;
         foreach my $field (@SeqFields) {
             next if ($field->{'selected'} ne 'yes');
@@ -1375,7 +1446,7 @@ sub write_headers {
     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 
+        # Use english for excel as I am not sure how well excel handles
         # other character sets....
         $excel_sheet->write($$rows_output,$$cols_output,
                             $field->{'title'},
@@ -1397,10 +1468,9 @@ sub write_headers {
 sub compute_statistics_on_sequence {
     my ($seq) = @_;
     my @Data;
-    foreach my $res (@{$seq->{'contents'}}) {
-        next if ($res->{'type'} ne 'assessment');
-        foreach my $part (@{$res->{'parts'}}) {
-            next if ($res->{'partdata'}->{$part}->{'Survey'});
+    foreach my $res (&Apache::lonstathelpers::get_resources($navmap,$seq)) {
+        foreach my $part (@{$res->parts}) {
+            next if (($res->is_survey($part)) || ($res->is_anonsurvey($part))) ;
             #
             # This is where all the work happens
             my $data = &get_statistics($seq,$res,$part,scalar(@StatsArray)+1);
@@ -1418,9 +1488,8 @@ sub compute_all_statistics {
         return;
     }
     my $c = $r->connection;
-    foreach my $seq (&Apache::lonstatistics::Sequences_with_Assess()) {
+    foreach my $seq (@sequences) {
         last if ($c->aborted);
-        next if ($seq->{'num_assess'} < 1);
         &compute_sequence_statistics($seq);
         &compute_statistics_on_sequence($seq);
     }
@@ -1490,13 +1559,13 @@ sub sort_data {
 
 =item &get_statistics()
 
-Wrapper routine from the call to loncoursedata::get_problem_statistics.  
+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
 
 Inputs: $sequence, $resource, $part, $problem_num
 
-Returns: Hash reference with statistics data from 
+Returns: Hash reference with statistics data from
 loncoursedata::get_problem_statistics.
 
 =cut
@@ -1507,46 +1576,55 @@ 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 $symb = $resource->symb;
+    my $courseid = $env{'request.course.id'};
     #
     my $data = &Apache::loncoursedata::get_problem_statistics
-                        (\@Apache::lonstatistics::SelectedSections,
+                        ([&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->{'title'};
-    $data->{'title'}       = $resource->{'title'};
-    $data->{'title.link'}  = $resource->{'src'}.'?symb='.
-        &Apache::lonnet::escape($resource->{'symb'});
+    $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'} = 
+        $data->{'deg_of_disc'} =
             &compute_discrimination_factor($resource,$part,$sequence);
     }
     #
     # Store in metadata if computations were done for all students
     if ($data->{'num_students'} > 1) {
-        my @Sections = @Apache::lonstatistics::SelectedSections;
+        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 = 
+        $data->{'course'} = $env{'request.course.id'};
+        my $urlres=(&Apache::lonnet::decode_symb($resource->symb))[2];
+        my %storestats =
             &LONCAPA::lonmetadata::dynamic_metadata_storage($data);
-        my ($dom,$user) = $urlres=~/^(\w+)\/(\w+)/; 
+        my ($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);
+#    my $duedate = &Apache::lonnet::EXT('resource.'.$part.'.duedate',$symb);;
+#    my $opendate = &Apache::lonnet::EXT('resource.'.$part.'.opendate',$symb);
+#    my $maxtries = &Apache::lonnet::EXT('resource.'.$part.'.maxtries',$symb);
+#    my $hinttries = &Apache::lonnet::EXT('resource.'.$part.'.hinttries',$symb);
+    my $weight = &Apache::lonnet::EXT('resource.'.$part.'.weight',$symb);
+    $data->{'weight'} = $weight;
+#    $data->{'duedate'} = $duedate;
+#    $data->{'opendate'} = $opendate;
+#    $data->{'maxtries'} = $maxtries;
+#    $data->{'hinttries'} = $hinttries;
 #    $data->{'resptypes'} = join(',',@{$resource->{'partdata'}->{$part}->{'ResponseTypes'}});
     return $data;
 }
@@ -1567,40 +1645,42 @@ Returns: integer between -1 and 1
 ###############################################
 ###############################################
 sub compute_discrimination_factor {
-    my ($resource,$part,$sequence) = @_;
+    my ($resource,$part,$seq) = @_;
+    my $symb = $resource->symb;
     my @Resources;
-    foreach my $res (@{$sequence->{'contents'}}) {
-        next if ($res->{'symb'} eq $resource->{'symb'});
-        push (@Resources,$res->{'symb'});
+    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 = 
+    my $ranking =
         &Apache::loncoursedata::rank_students_by_scores_on_resources
         (\@Resources,
-         \@Apache::lonstatistics::SelectedSections,
+         [&Apache::lonstatistics::get_selected_sections()],
+         [&Apache::lonstatistics::get_selected_groups()],
          $Apache::lonstatistics::enrollment_status,undef,
-         $starttime,$endtime);
+         $starttime,$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()]; 
+    my @BottomSet = map { $_->[&Apache::loncoursedata::RNK_student()];
                       } @{$ranking}[0..$number_to_grab];
-    my @TopSet    = 
-        map { 
-            $_->[&Apache::loncoursedata::RNK_student()]; 
-          } @{$ranking}[($num_students-$number_to_grab)..($num_students-1)];
+    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,$bottom_max) = 
-        &Apache::loncoursedata::get_sum_of_scores($resource,$part,\@BottomSet,
+    my ($bottom_sum,$bottom_max) =
+        &Apache::loncoursedata::get_sum_of_scores($symb,$part,\@BottomSet,
                                                   undef,$starttime,$endtime);
-    my ($top_sum,$top_max) = 
-        &Apache::loncoursedata::get_sum_of_scores($resource,$part,\@TopSet,
+    my ($top_sum,$top_max) =
+        &Apache::loncoursedata::get_sum_of_scores($symb,$part,\@TopSet,
                                                   undef,$starttime,$endtime);
     my $deg_of_disc;
     if ($top_max == 0 || $bottom_max==0) {
@@ -1622,31 +1702,33 @@ sub compute_discrimination_factor {
 ##
 ## K=the number of items in your test
 ## M=the mean score on the test
-## s=the standard deviation of the scores on your test 
+## s=the standard deviation of the scores on your test
 ##
 ## then:
-## 
+##
 ## KR-21 rk= [K/(K-1)] * [1- (M*(K-M))/(K*s^2))]
 ##
 ###############################################
 ###############################################
 sub compute_sequence_statistics {
     my ($seq) = @_;
-    my $symb = $seq->{'symb'};
+    my $symb = $seq->symb;
     my @Resources;
-    foreach my $res (@{$seq->{'contents'}}) {
-        next if ($res->{'type'} ne 'assessment');
-        push (@Resources,$res->{'symb'});
+    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) = 
+    my ($smin,$smax,$sMean,$sSTD,$scount,$sMAX) =
         &Apache::loncoursedata::score_stats
-                    (\@Apache::lonstatistics::SelectedSections,
+                    ([&Apache::lonstatistics::get_selected_sections()],
+                     [&Apache::lonstatistics::get_selected_groups()],
                      $Apache::lonstatistics::enrollment_status,
                      \@Resources,$starttime,$endtime,undef);
-    $SeqStat{$symb}->{'title'}  = $seq->{'title'};
+    $SeqStat{$symb}->{'title'}  = $seq->compTitle;
     $SeqStat{$symb}->{'scoremax'}  = $smax;
     $SeqStat{$symb}->{'scoremin'}  = $smin;
     $SeqStat{$symb}->{'scoremean'} = $sMean;
@@ -1655,13 +1737,14 @@ sub compute_sequence_statistics {
     $SeqStat{$symb}->{'max_possible'} = $sMAX;
     #
     # Compute statistics based on the number of correct problems
-    # 'correct' is taken to mean 
+    # 'correct' is taken to mean
     my ($cmin,$cmax,$cMean,$cSTD,$ccount)=
         &Apache::loncoursedata::count_stats
-        (\@Apache::lonstatistics::SelectedSections,
+        ([&Apache::lonstatistics::get_selected_sections()],
+         [&Apache::lonstatistics::get_selected_groups()],
          $Apache::lonstatistics::enrollment_status,
          \@Resources,$starttime,$endtime,undef);
-    my $K = $seq->{'num_assess_parts'};
+    my $K = $part_count;
     my $kr_21;
     if ($K > 1 && $cSTD > 0) {
         $kr_21 =  ($K/($K-1)) * (1 - $cMean*($K-$cMean)/($K*$cSTD**2));