--- loncom/interface/statistics/lonproblemstatistics.pm	2005/03/10 17:33:57	1.101
+++ loncom/interface/statistics/lonproblemstatistics.pm	2006/05/01 19:29:13	1.107
@@ -1,6 +1,6 @@
 # The LearningOnline Network with CAPA
 #
-# $Id: lonproblemstatistics.pm,v 1.101 2005/03/10 17:33:57 matthew Exp $
+# $Id: lonproblemstatistics.pm,v 1.107 2006/05/01 19:29:13 albertel 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;
@@ -516,35 +516,35 @@ 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)
@@ -559,7 +559,7 @@ 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'}}++;
@@ -608,8 +608,8 @@ sub CreateInterface {
     &parse_field_selection();
     #
     my $Str = '';
-    $Str .= &Apache::lonhtmlcommon::breadcrumbs
-        (undef,'Overall Problem Statistics','Statistics_Overall_Key');
+    $Str .= &Apache::lonhtmlcommon::breadcrumbs('Overall Problem Statistics',
+						'Statistics_Overall_Key');
     $Str .= '<table cellspacing="5">'."\n";
     $Str .= '<tr>';
     $Str .= '<td align="center"><b>'.&mt('Sections').'</b></td>';
@@ -661,6 +661,11 @@ Main interface to problem statistics.
 my $navmap;
 my @sequences;
 
+sub clean_up {
+    undef($navmap);
+    undef(@sequences);
+}
+
 sub BuildProblemStatisticsPage {
     my ($r,$c)=@_;
     undef($navmap);
@@ -686,7 +691,7 @@ sub BuildProblemStatisticsPage {
     # Finally let the user know we are here
     my $interface = &CreateInterface($r);
     $r->print($interface);
-    $r->print('<input type="hidden" name="sortby" value="'.$ENV{'form.sortby'}.
+    $r->print('<input type="hidden" name="sortby" value="'.$env{'form.sortby'}.
               '" />');
     #
     my @CacheButtonHTML = 
@@ -697,7 +702,7 @@ sub BuildProblemStatisticsPage {
     }
     #
     $r->print($Str);
-    if (! exists($ENV{'form.firstrun'})) {
+    if (! exists($env{'form.firstrun'})) {
         $r->print('<h3>'.
                   &mt('Press "Generate Statistics" when you are ready.').
                   '</h3><p>'.
@@ -705,6 +710,7 @@ sub BuildProblemStatisticsPage {
                       'for the first analysis.  Future analysis this session '.
                       ' will not have this delay.').
                   '</p>');
+	&clean_up();
         return;
     }
     $r->rflush();
@@ -718,14 +724,21 @@ sub BuildProblemStatisticsPage {
     if (! ref($navmap)) {
         $r->print('<h1>'.&mt('A course-wide error occured.').'</h1>'.
                   '<h3>'.$navmap.'</h3>');
+	&clean_up();
         return;
     }
-    if (exists($ENV{'form.Excel'})) {
+    if (exists($env{'form.Excel'})) {
+        $r->print('<h4>'.
+                  &Apache::lonstatistics::section_and_enrollment_description().
+                  '</h4>');
         &Excel_output($r);
     } else { 
         $r->print('<input type="submit" name="Excel" value="'.
                   &mt('Produce Excel Output').'" />'.'&nbsp;'x5);
         $r->rflush();
+        $r->print('<h4>'.
+                  &Apache::lonstatistics::section_and_enrollment_description().
+                  '</h4>');
         my $count = 0;
         foreach my $seq (@sequences) {
             my @resources = 
@@ -742,9 +755,9 @@ sub BuildProblemStatisticsPage {
             $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);
         }
@@ -759,6 +772,7 @@ sub BuildProblemStatisticsPage {
             &output_sequence_statistics($r);
         }
     }
+    &clean_up();
     return;
 }
 
@@ -819,7 +833,7 @@ 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) {
@@ -841,7 +855,7 @@ sub output_html_stats {
 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)) {
@@ -965,7 +979,7 @@ 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') {
@@ -1219,8 +1233,8 @@ END
 sub plot_dropdown {
     my $current = '';
     #
-    if (defined($ENV{'form.plot'})) {
-        $current = $ENV{'form.plot'};
+    if (defined($env{'form.plot'})) {
+        $current = $env{'form.plot'};
     }
     #
     my @Additional_Plots = (
@@ -1273,7 +1287,7 @@ sub Excel_output {
     return if (! defined($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);
     }
@@ -1286,17 +1300,16 @@ 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());
     #
     # Time restrictions
     my $time_string;
@@ -1534,10 +1547,10 @@ sub get_statistics {
     #
     my ($starttime,$endtime) = &Apache::lonstathelpers::get_time_limits();
     my $symb = $resource->symb;
-    my $courseid = $ENV{'request.course.id'};
+    my $courseid = $env{'request.course.id'};
     #
     my $data = &Apache::loncoursedata::get_problem_statistics
-                        (\@Apache::lonstatistics::SelectedSections,
+                        ([&Apache::lonstatistics::get_selected_sections()],
                          $Apache::lonstatistics::enrollment_status,
                          $symb,$part,$courseid,$starttime,$endtime);
     $data->{'symb'}        = $symb;
@@ -1555,11 +1568,11 @@ sub get_statistics {
     #
     # Store in metadata if computations were done for all students
     if ($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'};
+        $data->{'course'} = $env{'request.course.id'};
         my $urlres=(&Apache::lonnet::decode_symb($resource->symb))[2];
         $data->{'urlres'}=$urlres;
         my %storestats = 
@@ -1615,9 +1628,9 @@ sub compute_discrimination_factor {
     my $ranking = 
         &Apache::loncoursedata::rank_students_by_scores_on_resources
         (\@Resources,
-         \@Apache::lonstatistics::SelectedSections,
+         [&Apache::lonstatistics::get_selected_sections()],
          $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);
@@ -1627,7 +1640,7 @@ sub compute_discrimination_factor {
     my @TopSet    = 
         map { 
             $_->[&Apache::loncoursedata::RNK_student()]; 
-          } @{$ranking}[($num_students-$number_to_grab)..($num_students-1)];
+          } @{$ranking}[-$number_to_grab..0];
     if (! @BottomSet || (@BottomSet == 1 && $BottomSet[0] eq '') ||
         ! @TopSet    || (@TopSet    == 1 && $TopSet[0]    eq '')) {
         return 'nan';
@@ -1680,7 +1693,7 @@ sub compute_sequence_statistics {
     # First compute statistics based on student scores
     my ($smin,$smax,$sMean,$sSTD,$scount,$sMAX) = 
         &Apache::loncoursedata::score_stats
-                    (\@Apache::lonstatistics::SelectedSections,
+                    ([&Apache::lonstatistics::get_selected_sections()],
                      $Apache::lonstatistics::enrollment_status,
                      \@Resources,$starttime,$endtime,undef);
     $SeqStat{$symb}->{'title'}  = $seq->compTitle;
@@ -1695,7 +1708,7 @@ sub compute_sequence_statistics {
     # 'correct' is taken to mean 
     my ($cmin,$cmax,$cMean,$cSTD,$ccount)=
         &Apache::loncoursedata::count_stats
-        (\@Apache::lonstatistics::SelectedSections,
+        ([&Apache::lonstatistics::get_selected_sections()],
          $Apache::lonstatistics::enrollment_status,
          \@Resources,$starttime,$endtime,undef);
     my $K = $part_count;