# The LearningOnline Network with CAPA
#
# $Id: lonproblemanalysis.pm,v 1.42 2003/10/17 22:05:45 matthew Exp $
#
# Copyright Michigan State University Board of Trustees
#
# This file is part of the LearningOnline Network with CAPA (LON-CAPA).
#
# LON-CAPA is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# LON-CAPA is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with LON-CAPA; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#
# /home/httpd/html/adm/gpl.txt
#
# http://www.lon-capa.org/
#

package Apache::lonproblemanalysis;

use strict;
use Apache::lonnet();
use Apache::loncommon();
use Apache::lonhtmlcommon();
use Apache::loncoursedata();
use Apache::lonstatistics;
use Apache::lonlocal;
use HTML::Entities();
use Time::Local();

my $plotcolors = ['#33ff00', 
                  '#0033cc', '#990000', '#aaaa66', '#663399', '#ff9933',
                  '#66ccff', '#ff9999', '#cccc33', '#660000', '#33cc66',
                  ]; 

sub BuildProblemAnalysisPage {
    my ($r,$c)=@_;
    $r->print('<h2>'.&mt('Option Response Problem Analysis').'</h2>');
    $r->print(&CreateInterface());
    #
    my @Students = @Apache::lonstatistics::Students;
    #
    if (exists($ENV{'form.ClearCache'}) || 
        exists($ENV{'form.updatecaches'}) ||
        (exists($ENV{'form.firstanalysis'}) &&
         $ENV{'form.firstanalysis'} ne 'no')) {
        &Apache::lonstatistics::Gather_Full_Student_Data($r);
    }
    if (! exists($ENV{'form.firstanalysis'})) {
        $r->print('<input type="hidden" name="firstanalysis" value="yes" />');
    } else {
        $r->print('<input type="hidden" name="firstanalysis" value="no" />');
    }
    $r->rflush();
    if (exists($ENV{'form.problemchoice'}) && 
        ! exists($ENV{'form.SelectAnother'})) {
        $r->print('<input type="submit" name="ProblemAnalysis" value="'.
                  &mt('Analyze Problem Again').'" />');
        $r->print('&nbsp;'x5);
        $r->print('<input type="submit" name="ClearCache" value="'.
                  &mt('Clear Caches').'" />');
        $r->print('&nbsp;'x5);
        $r->print('<input type="submit" name="updatecaches" value="'.
                  &mt('Update Student Data').'" />');
        $r->print('&nbsp;'x5);
        $r->print('<input type="hidden" name="problemchoice" value="'.
                  $ENV{'form.problemchoice'}.'" />');
        $r->print('<input type="submit" name="SelectAnother" value="'.
                  &mt('Choose a different resource').'" />');
        $r->print('&nbsp;'x5);
        #
        $r->print('<hr />');
        #
        my ($symb,$part,$resid) = &get_problem_symb(
                     &Apache::lonnet::unescape($ENV{'form.problemchoice'})
                                           );
        #
        my $resource = &get_resource_from_symb($symb);
        if (defined($resource)) {
            $r->print('<h3>'.$resource->{'src'}.'</h3>');
            my %Data = &get_problem_data($resource->{'src'});
            my $ORdata = $Data{$part.'.'.$resid};
            ##
            ## Render the problem
            my $base;
            ($base,undef) = ($resource->{'src'} =~ m|(.*/)[^/]*$|);
            $base = "http://".$ENV{'SERVER_NAME'}.$base;
            my $rendered_problem = 
                &Apache::lonnet::ssi_body($resource->{'src'});
            $rendered_problem =~ s/<\s*form\s*/<nop /g;
            $rendered_problem =~ s|(<\s*/form\s*>)|<\/nop>|g;
            $r->print('<table bgcolor="ffffff"><tr><td>'.
                      '<base href="'.$base.'" />'.
                      $rendered_problem.
                      '</td></tr></table>');
            ##
            ## Analyze the problem
            my $PerformanceData = 
                &Apache::loncoursedata::get_optionresponse_data
                                           (\@Students,$symb,$resid);
            if (defined($PerformanceData) && 
                ref($PerformanceData) eq 'ARRAY') {
                if ($ENV{'form.AnalyzeOver'} eq 'Tries') {
                    my $analysis_html = &tries_analysis($PerformanceData,
                                                         $ORdata);
                    $r->print($analysis_html);
                } elsif ($ENV{'form.AnalyzeOver'} eq 'Time') {
                    my $analysis_html = &time_analysis($PerformanceData,
                                                         $ORdata);
                $r->print($analysis_html);
                } else {
                    $r->print('<h2>'.
                              &mt('The analysis you have selected is '.
                                         'not supported at this time').
                              '</h2>');
                }
            } else {
                $r->print('<h2>'.
                          &mt('There is no student data for this problem.').
                          '</h2>');
            }
        } else {
            $r->print('resource is undefined');
        }
        $r->print('<hr />');
    } else {
        $r->print('<input type="submit" name="ProblemAnalysis" value="'.
                  &mt('Analyze Problem').'" />');
        $r->print('&nbsp;'x5);
        $r->print('<h3>'.&mt('Please select a problem to analyze').'</h3>');
        $r->print(&OptionResponseProblemSelector());
    }
}

#########################################################
#########################################################
##
##      Misc interface routines use by analysis code
##
#########################################################
#########################################################
sub build_foil_index {
    my ($ORdata) = @_;
    return if (! exists($ORdata->{'Foils'}));
    my %Foildata = %{$ORdata->{'Foils'}};
    my @Foils = sort(keys(%Foildata));
    my %Concepts;
    foreach my $foilid (@Foils) {
        push(@{$Concepts{$Foildata{$foilid}->{'Concept'}}},
             $foilid);
    }
    undef(@Foils);
    # Having gathered the concept information in a hash, we now translate it
    # into an array because we need to be consistent about order.
    # Also put the foils in order, too.
    my $sortfunction = sub {
        my %Numbers = (one   => 1,
                       two   => 2,
                       three => 3,
                       four  => 4,
                       five  => 5,
                       six   => 6,
                       seven => 7,
                       eight => 8,
                       nine  => 9,
                       ten   => 10,);
        my $a1 = $a; 
        my $b1 = $b;
        if (exists($Numbers{lc($a)})) {
            $a1 = $Numbers{lc($a)};
        }
        if (exists($Numbers{lc($b)})) {
            $b1 = $Numbers{lc($b)};
        }
        $a1 cmp $b1;
    };
    my @Concepts;
    foreach my $concept (sort $sortfunction (keys(%Concepts))) {
        push(@Concepts,{ name => $concept,
                        foils => [@{$Concepts{$concept}}]});
        push(@Foils,(@{$Concepts{$concept}}));
    }
    #
    # Build up the table of row labels.
    my $table = '<table border="1" >'."\n";
    if (@Concepts > 1) {
        $table .= '<tr>'.
            '<th>'.&mt('Concept Number').'</th>'.
            '<th>'.&mt('Concept').'</th>'.
            '<th>'.&mt('Foil Number').'</th>'.
            '<th>'.&mt('Foil Name').'</th>'.
            '<th>'.&mt('Foil Text').'</th>'.
            '<th>'.&mt('Correct Value').'</th>'.
            "</tr>\n";
    } else {
        $table .= '<tr>'.
            '<th>'.&mt('Foil Number').'</th>'.
            '<th>'.&mt('Foil Name').'</th>'.
            '<th>'.&mt('Foil Text').'</th>'.
            '<th>'.&mt('Correct Value').'</th>'.
            "</tr>\n";
    }        
    my $conceptindex = 1;
    my $foilindex = 1;
    foreach my $concept (@Concepts) {
        my @FoilsInConcept = @{$concept->{'foils'}};
        my $firstfoil = shift(@FoilsInConcept);
        if (@Concepts > 1) {
            $table .= '<tr>'.
                '<td>'.$conceptindex.'</td>'.
                '<td>'.$concept->{'name'}.'</td>'.
                '<td>'.$foilindex++.'</td>'.
                '<td>'.$Foildata{$firstfoil}->{'name'}.'</td>'.
                '<td>'.$Foildata{$firstfoil}->{'text'}.'</td>'.
                '<td>'.$Foildata{$firstfoil}->{'value'}.'</td>'.
                "</tr>\n";
        } else {
            $table .= '<tr>'.
                '<td>'.$foilindex++.'</td>'.
                '<td>'.$Foildata{$firstfoil}->{'name'}.'</td>'.
                '<td>'.$Foildata{$firstfoil}->{'text'}.'</td>'.
                '<td>'.$Foildata{$firstfoil}->{'value'}.'</td>'.
                "</tr>\n";
        }
        foreach my $foilid (@FoilsInConcept) {
            if (@Concepts > 1) {
                $table .= '<tr>'.
                    '<td></td>'.
                    '<td></td>'.
                    '<td>'.$foilindex.'</td>'.
                    '<td>'.$Foildata{$foilid}->{'name'}.'</td>'.
                    '<td>'.$Foildata{$foilid}->{'text'}.'</td>'.
                    '<td>'.$Foildata{$foilid}->{'value'}.'</td>'.
                    "</tr>\n";
            } else {
                $table .= '<tr>'.
                    '<td>'.$foilindex.'</td>'.
                    '<td>'.$Foildata{$foilid}->{'name'}.'</td>'.
                    '<td>'.$Foildata{$foilid}->{'text'}.'</td>'.
                    '<td>'.$Foildata{$foilid}->{'value'}.'</td>'.
                    "</tr>\n";
            }                
        } continue {
            $foilindex++;
        }
    } continue {
        $conceptindex++;
    }
    $table .= "</table>\n";
    #
    # Build option index with color stuff
    return ($table,\@Foils,\@Concepts);
}

sub build_option_index {
    my ($ORdata)= @_;
    my $table = "<table>\n";
    my $optionindex = 0;
    my @Rows;
    foreach my $option (&mt('correct option chosen'),@{$ORdata->{'Options'}}) {
        push (@Rows,
              '<tr>'.
              '<td bgcolor="'.$plotcolors->[$optionindex++].'">'.
              ('&nbsp;'x4).'</td>'.
              '<td>'.$option.'</td>'.
              "</tr>\n");
    }
    shift(@Rows); # Throw away 'correct option chosen' color
    $table .= join('',reverse(@Rows));
    $table .= "</table>\n";
}

#########################################################
#########################################################
##
##         Tries Analysis
##
#########################################################
#########################################################
sub tries_analysis {
    my ($PerformanceData,$ORdata) = @_;
    my $mintries = 1;
    my $maxtries = $ENV{'form.NumPlots'};
    my ($table,$Foils,$Concepts) = &build_foil_index($ORdata);
    if ((@$Concepts < 2) && ($ENV{'form.AnalyzeAs'} ne 'Foils')) {
        $table = '<h3>'.
            &mt('Not enough data for concept analysis.  '.
                'Performing Foil Analysis').
            '</h3>'.$table;
        $ENV{'form.AnalyzeAs'} = 'Foils';
    }
    my %ResponseData = &analyze_option_data_by_tries($PerformanceData,
                                                     $mintries,$maxtries);
    my $analysis = '';
    if ($ENV{'form.AnalyzeAs'} eq 'Foils') {
        $analysis = &Tries_Foil_Analysis($mintries,$maxtries,$Foils,
                                         \%ResponseData,$ORdata);
    } else {
        $analysis = &Tries_Concept_Analysis($mintries,$maxtries,
                                            $Concepts,\%ResponseData,$ORdata);
    }
    $table .= $analysis;
    return $table;
}

sub Tries_Foil_Analysis {
    my ($mintries,$maxtries,$Foils,$respdat,$ORdata) = @_;
    my %ResponseData = %$respdat;
    #
    # Compute the data neccessary to make the plots
    my @PlotData; 
    foreach my $foilid (@$Foils) {
        for (my $i=$mintries;$i<=$maxtries;$i++) {
            if ($ResponseData{$foilid}->[$i]->{'_total'} == 0) {
                push(@{$PlotData[$i]->{'_correct'}},0);
            } else {
                push(@{$PlotData[$i]->{'_correct'}},
                     100*$ResponseData{$foilid}->[$i]->{'_correct'}/
                     $ResponseData{$foilid}->[$i]->{'_total'});
            }
            foreach my $option (@{$ORdata->{'Options'}}) {
                push(@{$PlotData[$i]->{'_total'}},
                     $ResponseData{$foilid}->[$i]->{'_total'});
                if ($ResponseData{$foilid}->[$i]->{'_total'} == 0) {
                    push (@{$PlotData[$i]->{$option}},0);
                } else {
                    if ($ResponseData{$foilid}->[$i]->{'_total'} ==
                        $ResponseData{$foilid}->[$i]->{'_correct'}) {
                        push(@{$PlotData[$i]->{$option}},0);
                    } else {
                        push (@{$PlotData[$i]->{$option}},
                              100 * $ResponseData{$foilid}->[$i]->{$option} / 
                              ($ResponseData{$foilid}->[$i]->{'_total'} - 
                               $ResponseData{$foilid}->[$i]->{'_correct'}));
                    }
                }
            }
        }
    }
    # 
    # Build a table for the plots
    my $analysis_html = "<table>\n";
    my $foilkey = &build_option_index($ORdata);
    for (my $i=$mintries;$i<=$maxtries;$i++) {
        my $count = $ResponseData{'_total'}->[$i];
        if ($count == 0) {
            $count = 'no submissions';
        } elsif ($count == 1) {
            $count = '1 submission';
        } else {
            $count = $count.' submissions';
        }
        my $title = 'Attempt '.$i.', '.$count;
        my @Datasets;
        foreach my $option ('_correct',@{$ORdata->{'Options'}}) {
            next if (! exists($PlotData[$i]->{$option}));
            push(@Datasets,$PlotData[$i]->{$option});
        }
        my $correctgraph = &Apache::loncommon::DrawGraph
            ($title,'Foil Number','Percent Correct',
             100,$plotcolors,$Datasets[0]);
        $analysis_html.= '<tr><td>'.$correctgraph.'</td>';
        ##
        ##
        for (my $i=0; $i< scalar(@{$Datasets[0]});$i++) {
            $Datasets[0]->[$i]=0;
        }
        $count = $ResponseData{'_total'}->[$i]-$ResponseData{'_correct'}->[$i];
        if ($count == 0) {
            $count = 'no submissions';
        } elsif ($count == 1) {
            $count = '1 submission';
        } else {
            $count = $count.' submissions';
        }
        $title = 'Attempt '.$i.', '.$count;
        my $incorrectgraph = &Apache::loncommon::DrawGraph
            ($title,'Foil Number','% Option Chosen Incorrectly',
             100,$plotcolors,@Datasets);
        $analysis_html.= '<td>'.$incorrectgraph.'</td>';
        $analysis_html.= '<td>'.$foilkey."<td></tr>\n";
    }
    $analysis_html .= "</table>\n";
    return $analysis_html;
}

sub Tries_Concept_Analysis {
    my ($mintries,$maxtries,$Concepts,$respdat,$ORdata) = @_;
    my %ResponseData = %$respdat;
    my $analysis_html = "<table>\n";
    #
    # Compute the data neccessary to make the plots
    my @PlotData;
    # Concept analysis
    #
    # Note: we do not bother with characterizing the students incorrect
    # answers at the concept level because an incorrect answer for one foil
    # may be a correct answer for another foil.
    my %ConceptData;
    foreach my $concept (@{$Concepts}) {
        for (my $i=$mintries;$i<=$maxtries;$i++) {
            #
            # Gather the per-attempt data
            my $cdata = $ConceptData{$concept}->[$i];
            foreach my $foilid (@{$concept->{'foils'}}) {
                $cdata->{'_correct'} += 
                    $ResponseData{$foilid}->[$i]->{'_correct'};
                $cdata->{'_total'}   += 
                    $ResponseData{$foilid}->[$i]->{'_total'};
            }
            push (@{$PlotData[$i]->{'_total'}},$cdata->{'_total'});
            if ($cdata->{'_total'} == 0) {
                push (@{$PlotData[$i]->{'_correct'}},0);
            } else {
                push (@{$PlotData[$i]->{'_correct'}},
                      100*$cdata->{'_correct'}/$cdata->{'_total'});
                }
        }
    }
    # Build a table for the plots
    for (my $i=$mintries;$i<=$maxtries;$i++) {
        my $minstu = $PlotData[$i]->{'_total'}->[0];
        my $maxstu = $PlotData[$i]->{'_total'}->[0];
        foreach my $count (@{$PlotData[$i]->{'_total'}}) {
            if ($minstu > $count) {
                $minstu = $count;
            }
            if ($maxstu < $count) {
                $maxstu = $count;
            }
        }
        $maxstu = 0 if (! defined($maxstu));
        $minstu = 0 if (! defined($minstu));
        my $title;
        my $count = $ResponseData{'_total'}->[$i];
        if ($count == 0) {
            $count = 'no submissions';
        } elsif ($count == 1) {
            $count = '1 submission';
        } else {
            $count = $count.' submissions';
        }
        $title = 'Attempt '.$i.', '.$count;
        my $graphlink = &Apache::loncommon::DrawGraph
            ($title,'Concept Number','Percent Correct',
             100,$plotcolors,$PlotData[$i]->{'_correct'});
        $analysis_html.= '<tr><td>'.$graphlink."</td></tr>\n";
    }
    $analysis_html .= "</table>\n";
    return $analysis_html;
}

sub analyze_option_data_by_tries {
    my ($PerformanceData,$mintries,$maxtries) = @_;
    my %Trydata;
    $mintries = 1         if (! defined($mintries) || $mintries < 1);
    $maxtries = $mintries if (! defined($maxtries) || $maxtries < $mintries);
    foreach my $row (@$PerformanceData) {
        next if (! defined($row));
        my $tries = &get_tries_from_row($row);
        my %Row   = &Process_Row($row);
        while (my ($foilid,$href) = each(%Row)) {
            if (! ref($href)) { 
                $Trydata{$foilid}->[$tries] += $href;
                next;
            }
            while (my ($option,$value) = each(%$href)) {
                $Trydata{$foilid}->[$tries]->{$option}+=$value;
            }
        }
    }
    return %Trydata;
}

#########################################################
#########################################################
##
##                 Time Analysis
##
#########################################################
#########################################################
sub time_analysis {
    my ($PerformanceData,$ORdata) = @_;
    my ($table,$Foils,$Concepts) = &build_foil_index($ORdata);
    if ((@$Concepts < 2) && ($ENV{'form.AnalyzeAs'} ne 'Foils')) {
        $table = '<h3>'.
            &mt('Not enough data for concept analysis.  '.
                'Performing Foil Analysis').
            '</h3>'.$table;
        $ENV{'form.AnalyzeAs'} = 'Foils';
    }
    my $num_plots = $ENV{'form.NumPlots'};
    my $num_data = scalar(@$PerformanceData)-1;
    my $percent = sprintf('%2f',100/$num_plots);
    #
    $table .= "<table>\n";
    for (my $i=0;$i<$num_plots;$i++) {
        ##
        my $starttime = &Apache::lonhtmlcommon::get_date_from_form
            ('startdate_'.$i);
        my $endtime = &Apache::lonhtmlcommon::get_date_from_form
            ('enddate_'.$i);
        if (! defined($starttime) || ! defined($endtime)) {
            my $sec_in_day = 86400;
            my $last_sub_time = &get_time_from_row($PerformanceData->[-1]);
            my ($sday,$smon,$syear);
            (undef,undef,undef,$sday,$smon,$syear) = 
                localtime($last_sub_time - $sec_in_day*$i);
            $starttime = &Time::Local::timelocal(0,0,0,$sday,$smon,$syear);
            $endtime = $starttime + $sec_in_day;
            if ($i == ($num_plots -1 )) {
                $starttime = &get_time_from_row($PerformanceData->[0]);
            }
        }
        my $startdateform = &Apache::lonhtmlcommon::date_setter
            ('Statistics','startdate_'.$i,$starttime);
        my $enddateform = &Apache::lonhtmlcommon::date_setter
            ('Statistics','enddate_'.$i,$endtime);
        #
        my $begin_index;
        my $end_index;
        my $j;
        while (++$j < scalar(@$PerformanceData)) {
            last if (&get_time_from_row($PerformanceData->[$j]) > $starttime);
        }
        $begin_index = $j;
        while (++$j < scalar(@$PerformanceData)) {
            last if (&get_time_from_row($PerformanceData->[$j]) > $endtime);
        }
        $end_index = $j;
        ##
        my $interval = {
            begin_index => $begin_index,
            end_index   => $end_index,
            startdateform => $startdateform,
            enddateform   => $enddateform,
        };
        if ($ENV{'form.AnalyzeAs'} eq 'Foils') {
            $table .= &Foil_Time_Analysis($PerformanceData,$ORdata,$Foils,
                                          $interval);
        } else {
            $table .= &Concept_Time_Analysis($PerformanceData,$ORdata,
                                             $Concepts,$interval);
        }
    }
    #
    return $table;
}

sub Foil_Time_Analysis {
    my ($PerformanceData,$ORdata,$Foils,$interval) = @_;
    my $analysis_html;
    my $foilkey = &build_option_index($ORdata);
    my ($begin_index,$end_index) = ($interval->{'begin_index'},
                                    $interval->{'end_index'});
    my %TimeData;
    #
    # Compute the number getting the foils correct or incorrects
    for (my $j=$begin_index;$j<=$end_index;$j++) {
        my $row = $PerformanceData->[$j];
        next if (! defined($row));
        my %Row = &Process_Row($row);
        while (my ($foilid,$href) = each(%Row)) {
            if (! ref($href)) {
                $TimeData{$foilid} += $href;
                next;
            }
            while (my ($option,$value) = each(%$href)) {
                $TimeData{$foilid}->{$option}+=$value;
            }
        }
    }
    my @Plotdata;
    foreach my $foil (@$Foils) {
        my $total = $TimeData{$foil}->{'_total'};
        if ($total == 0) {
            push(@{$Plotdata[0]},0);
        } else {
            push(@{$Plotdata[0]},
                 100 * $TimeData{$foil}->{'_correct'} / $total);
        }
        my $total_incorrect = $total - $TimeData{$foil}->{'_correct'};
        my $optionidx = 1;
        foreach my $option (@{$ORdata->{'Options'}}) {
            if ($total_incorrect == 0) {
                push(@{$Plotdata[$optionidx]},0);
            } else {
                push(@{$Plotdata[$optionidx]},
                     100 * $TimeData{$foil}->{$option} / $total_incorrect);
            }
        } continue {
            $optionidx++;
        }
    }
    #
    # Create the plot
    my $count = $end_index-$begin_index;
    my $title;
    if ($count == 0) {
        $title = 'no submissions';
    } elsif ($count == 1) {
        $title = 'one submission';
    } else {
        $title = $count.' submissions';
    }
    my $correctplot = &Apache::loncommon::DrawGraph($title,
                                                    'Foil Number',
                                                    'Percent Correct',
                                                    100,
                                                    $plotcolors,
                                                    $Plotdata[0]);
    for (my $j=0; $j< scalar(@{$Plotdata[0]});$j++) {
        $Plotdata[0]->[$j]=0;
    }
    $count = $end_index-$begin_index-$TimeData{'_correct'};
    if ($count == 0) {
        $title = 'no submissions';
    } elsif ($count == 1) {
        $title = 'one submission';
    } else {
        $title = $count.' submissions';
    }
    my $incorrectplot = &Apache::loncommon::DrawGraph($title,
                                                 'Foil Number',
                                                 'Incorrect Option Choice',
                                                 100,
                                                 $plotcolors,
                                                 @Plotdata);        
    $analysis_html.='<tr>'.
        '<td>'.$correctplot.'</td>'.
        '<td>'.$incorrectplot.'</td>'.
        '<td align="left" valign="top">'.$foilkey.'</td>'."</tr>\n";
    $analysis_html.= '<tr>'.'<td colspan="3">'.
        '<b>Start Time</b>:'.
        ' &nbsp;'.$interval->{'startdateform'}.'<br />'.
        '<b>End Time</b>&nbsp;&nbsp;: '.
        '&nbsp;'.$interval->{'enddateform'}.'<br />'.
#        '<b>Plot Title</b>&nbsp;&nbsp;:'.
#        ("&nbsp;"x3).$interval->{'titleform'}.
        '</td>'.
        "</tr>\n";
    return $analysis_html;
}

sub Concept_Time_Analysis {
    my ($PerformanceData,$ORdata,$Concepts,$interval) = @_;
    my $analysis_html;
    ##
    ## Determine starttime, endtime, startindex, endindex
    my ($begin_index,$end_index) = ($interval->{'begin_index'},
                                    $interval->{'end_index'});
    my %TimeData;
    #
    # Compute the number getting the foils correct or incorrects
    for (my $j=$begin_index;$j<=$end_index;$j++) {
        my $row = $PerformanceData->[$j];
        next if (! defined($row));
        my %Row = &Process_Row($row);
        while (my ($foilid,$href) = each(%Row)) {
            if (! ref($href)) {
                $TimeData{$foilid} += $href;
                next;
            }
            while (my ($option,$value) = each(%$href)) {
                $TimeData{$foilid}->{$option}+=$value;
            }
        }
    }
    #
    # Put the data in plottable form
    my @Plotdata;
    foreach my $concept (@$Concepts) {
        my ($total,$correct);
        foreach my $foil (@{$concept->{'foils'}}) {
            $total += $TimeData{$foil}->{'_total'};
            $correct += $TimeData{$foil}->{'_correct'};
        }
        if ($total == 0) {
            push(@Plotdata,0);
        } else {
            push(@Plotdata,100 * $correct / $total);
        }
    }
    #
    # Create the plot
    my $title = ($end_index - $begin_index).' submissions';
    my $correctplot = &Apache::loncommon::DrawGraph($title,
                                                    'Concept Number',
                                                    'Percent Correct',
                                                    100,
                                                    $plotcolors,
                                                    \@Plotdata);
    $analysis_html.='<tr>'.
        '<td>'.$correctplot.'</td>'.
        '<td align="left" valign="top">'.
        '<b>Start Time</b>: &nbsp;'.$interval->{'startdateform'}.'<br />'.
        '<b>End Time</b>&nbsp;&nbsp;: '.
           '&nbsp;'.$interval->{'enddateform'}.'<br />'.
#        '<b>Plot Title</b>&nbsp;&nbsp;:'.("&nbsp;"x3).
#            $interval->{'titleform'}.
        '</td>'.
        "</tr>\n";
    return $analysis_html;
}

#########################################################
#########################################################
##
##             Excel output 
##
#########################################################
#########################################################
sub prepare_excel_sheet {
    my ($PerformanceData,$ORdata) = @_;
    my (undef,$Foils,$Concepts) = &build_foil_index($ORdata);
}

sub process_data_for_excel_sheet {
    my ($PerformanceData,$Foils,$Concepts,$ORdata)=@_;
}

#########################################################
#########################################################
##
##             Interface 
##
#########################################################
#########################################################
sub CreateInterface {
    ##
    ## Environment variable initialization
    if (! exists$ENV{'form.AnalyzeOver'}) {
        $ENV{'form.AnalyzeOver'} = 'Tries';
    }
    ##
    ## Build the menu
    my $Str = '';
    $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">&nbsp;</td>';
    $Str .= '</tr>'."\n";
    ##
    ## 
    $Str .= '<tr><td align="center">'."\n";
    $Str .= &Apache::lonstatistics::SectionSelect('Section','multiple',5);
    $Str .= '</td>';
    #
    $Str .= '<td align="center">';
    $Str .= &Apache::lonhtmlcommon::StatusOptions(undef,undef,5);
    $Str .= '</td>';
    #
#    $Str .= '<td align="center">';
    my $only_seq_with_assessments = sub { 
        my $s=shift;
        if ($s->{'num_assess'} < 1) { 
            return 0;
        } else { 
            return 1;
        }
    };
    &Apache::lonstatistics::MapSelect('Maps','multiple,all',5,
                                              $only_seq_with_assessments);
    ##
    ##
    $Str .= '<td>';
    { # These braces are here to organize the code, not scope it.
        {
            $Str .= '<nobr>'.&mt('Analyze Over ');
            $Str .='<select name="AnalyzeOver" >';
            $Str .= '<option value="Tries" ';
            if (! exists($ENV{'form.AnalyzeOver'}) || 
                $ENV{'form.AnalyzeOver'} eq 'Tries'){
                # Default to Tries
                $Str .= ' selected ';
            }
            $Str .= '>'.&mt('Tries').'</option>';
            $Str .= '<option value="Time" ';
            $Str .= ' selected ' if ($ENV{'form.AnalyzeOver'} eq 'Time');
            $Str .= '>'.&mt('Time').'</option>';
            $Str .= '</select></nobr><br />';
        }
        {
            $Str .= '<nobr>'.&mt('Analyze as ');
            $Str .='<select name="AnalyzeAs" >';
            $Str .= '<option value="Concepts" ';
            if (! exists($ENV{'form.AnalyzeAs'}) || 
                $ENV{'form.AnalyzeAs'} eq 'Concepts'){
                # Default to Concepts
                $Str .= ' selected ';
            }
            $Str .= '>'.&mt('Concepts').'</option>';
            $Str .= '<option value="Foils" ';
            $Str .= ' selected ' if ($ENV{'form.AnalyzeAs'} eq 'Foils');
            $Str .= '>'.&mt('Foils').'</option>';
            $Str .= '</select></nobr><br />';
        }
        {
            $Str .= '<br /><nobr>'.&mt('Number of Plots:');
            $Str .= '<select name="NumPlots">';
            if (! exists($ENV{'form.NumPlots'}) 
                || $ENV{'form.NumPlots'} < 1 
                || $ENV{'form.NumPlots'} > 20) {
                $ENV{'form.NumPlots'} = 5;
            }
            foreach my $i (1,2,3,4,5,6,7,8,10,15,20) {
                $Str .= '<option value="'.$i.'" ';
                if ($ENV{'form.NumPlots'} == $i) { $Str.=' selected '; }
                $Str .= '>'.$i.'</option>';
            }
            $Str .= '</select></nobr>';
        }
    }
    $Str .= '</td>';
    ##
    ##
    $Str .= '</tr>'."\n";
    $Str .= '</table>'."\n";
    return $Str;
}

sub OptionResponseProblemSelector {
    my $Str;
    $Str = "\n<table>\n";
    foreach my $seq (&Apache::lonstatistics::Sequences_with_Assess()) {
        next if ($seq->{'num_assess'}<1);
        my $seq_str = '';
        foreach my $res (@{$seq->{'contents'}}) {
            next if ($res->{'type'} ne 'assessment');
            foreach my $part (@{$res->{'parts'}}) {
                my $partdata = $res->{'partdata'}->{$part};
                if (! exists($partdata->{'option'}) || 
                    $partdata->{'option'} == 0) {
                    next;
                }
                for (my $i=0;$i<scalar(@{$partdata->{'ResponseTypes'}});$i++){
                    my $respid = $partdata->{'ResponseIds'}->[$i];
                    my $resptype = $partdata->{'ResponseTypes'}->[$i];
                    if ($resptype eq 'option') {
                        my $value = &Apache::lonnet::escape($res->{'symb'}.':'.$part.':'.$respid);
                        my $checked = '';
                        if ($ENV{'form.problemchoice'} eq $value) {
                            $checked = 'checked ';
                        }
                        $seq_str .= '<tr><td>'.
  '<input type="radio" name="problemchoice" value="'.$value.'" '.$checked.'/>'.
  '</td><td>'.
  '<a href="'.$res->{'src'}.'">'.$res->{'title'}.'</a> ';
                        if ($partdata->{'option'} > 1) {
                            $seq_str .= &mt('response').' '.$respid;
                        }
                        $seq_str .= "</td></tr>\n";
                    }
                }
            }
        }
        if ($seq_str ne '') {
            $Str .= '<tr><td>&nbsp</td><td><b>'.$seq->{'title'}.'</b></td>'.
                "</tr>\n".$seq_str;
        }
    }
    $Str .= "</table>\n";
    return $Str;
}

#########################################################
#########################################################
##
##              Misc functions
##
#########################################################
#########################################################
sub get_problem_symb {
    my $problemstring = shift();
    my ($symb,$partid,$resid) = ($problemstring=~ /^(.*):([^:]*):([^:]*)$/);
    return ($symb,$partid,$resid);
}

sub get_resource_from_symb {
    my ($symb) = @_;
    foreach my $seq (&Apache::lonstatistics::Sequences_with_Assess()) {
        foreach my $res (@{$seq->{'contents'}}) {
            if ($res->{'symb'} eq $symb) {
                return $res;
            }
        }
    }
    return undef;
}

sub get_time_from_row {
    my ($row) = @_;
    if (ref($row)) {
        return $row->[3];
    } 
    return undef;
}

sub get_tries_from_row {
    my ($row) = @_;
    if (ref($row)) {
        return $row->[4];
    }
    return undef;
}

sub Process_Row {
    my ($row) = @_;
    my %RowData;
    my ($award,$grading,$submission,$time,$tries) = @$row;
    next if ($award eq 'MISSING_ANSWER');
    if ($award =~ /(APPROX_ANS|EXACT_ANS)/) {
        $RowData{'_correct'} = 1;
    }
    $RowData{'_total'} = 1;
    my @Foilgrades = split('&',$grading);
    my @Foilsubs   = split('&',$submission);
    for (my $j=0;$j<=$#Foilgrades;$j++) {
        my ($foilid,$correct)  = split('=',$Foilgrades[$j]);
        my (undef,$submission) = split('=',$Foilsubs[$j]);
        if ($correct) {
            $RowData{$foilid}->{'_correct'}++;
        } else {
            $submission = &Apache::lonnet::unescape($submission);
            $submission =~ s/\%20/ /g;
            $RowData{$foilid}->{$submission}++;
        }
        $RowData{$foilid}->{'_total'}++;
    }
    return %RowData;
}

##
## get problem data and put it into a useful data structure.
## note: we must force each foil and option to not begin or end with
##       spaces as they are stored without such data.
##
sub get_problem_data {
    my ($url) = @_;
    my $Answ=&Apache::lonnet::ssi($url,('grade_target' => 'analyze'));
    (my $garbage,$Answ)=split(/_HASH_REF__/,$Answ,2);
    my %Answer;
    %Answer=&Apache::lonnet::str2hash($Answ);
    my %Partdata;
    foreach my $part (@{$Answer{'parts'}}) {
        while (my($key,$value) = each(%Answer)) {
            next if ($key !~ /^$part/);
            $key =~ s/^$part\.//;
            if (ref($value) eq 'ARRAY') {
                if ($key eq 'options') {
                    $Partdata{$part}->{'Options'}=$value;
                } elsif ($key eq 'concepts') {
                    $Partdata{$part}->{'Concepts'}=$value;
                } elsif ($key =~ /^concept\.(.*)$/) {
                    my $concept = $1;
                    foreach my $foil (@$value) {
                        $Partdata{$part}->{'Foils'}->{$foil}->{'Concept'}=
                                                                      $concept;
                    }
                }
            } else {
                if ($key=~ /^foil\.text\.(.*)$/) {
                    my $foil = $1;
                    $Partdata{$part}->{'Foils'}->{$foil}->{'name'}=$foil;
                    $Partdata{$part}->{'Foils'}->{$foil}->{'text'}=$value;
                } elsif ($key =~ /^foil\.value\.(.*)$/) {
                    my $foil = $1;
                    $Partdata{$part}->{'Foils'}->{$foil}->{'value'}=$value;
                }
            }
        }
    }
    return %Partdata;
}

1;

__END__