# The LearningOnline Network with CAPA
#
# $Id: lonproblemstatistics.pm,v 1.42 2003/03/26 15:19:16 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/
#
# (Navigate problems for statistical reports
#
###

package Apache::lonproblemstatistics;

use strict;
use Apache::lonnet();
use Apache::lonhtmlcommon;
use Apache::loncoursedata;
use Apache::lonstatistics;

#######################################################
#######################################################

sub CreateInterface {
    my $Str = '';
    $Str .= '<table cellspacing="5">'."\n";
    $Str .= '<tr>';
    $Str .= '<td align="center"><b>Sections</b></td>';
    $Str .= '<td align="center"><b>Sequences and Folders</b></td>';
    $Str .= '<td align="center"><b>Output</b></td>';
    $Str .= '</tr>'."\n";
    #
    $Str .= '<tr><td align="center">'."\n";
    $Str .= &Apache::lonstatistics::SectionSelect('Section','multiple',5);
    $Str .= '</td><td align="center">';
    #
    my $only_seq_with_assessments = sub { 
        my $s=shift;
        if ($s->{'num_assess'} < 1) { 
            return 0;
        } else { 
            return 1;
        }
    };
    $Str .= &Apache::lonstatistics::MapSelect('Maps','multiple,all',5,
                                              $only_seq_with_assessments);
    $Str .= '</td><td>'."\n";
    $Str .= &CreateAndParseOutputSelector();
    $Str .= '</td></tr>'."\n";
    $Str .= '</table>'."\n";
    return $Str;
}

#######################################################
#######################################################

=pod

=item &CreateAndParseOutputSelector()

=cut

#######################################################
#######################################################
my $output_mode;
my $show;

my @OutputOptions = 
    (
     { name  => 'problem statistics grouped by sequence',
       value => 'HTML problem statistics grouped',
       description => 'Output statistics for the problem parts.',
       mode => 'html',
       show => 'grouped',
     },
     { name  => 'problem statistics ungrouped',
       value => 'HTML problem statistics ungrouped',
       description => 'Output statistics for the problem parts.',
       mode => 'html',
       show => 'ungrouped',
     },
     { name  => 'problem statistics, Excel',
       value => 'Excel problem statistics',
       description => 'Output statistics for the problem parts '.
           'in an Excel workbook',
       mode => 'excel',
       show => 'all',
     },
     { name  => 'Degree of Difficulty Plot',
       value => 'plot deg diff',
       description => 'Generate a plot of the degree of difficulty of each '.
           'problem part.',
       mode => 'plot',
       show => 'deg of diff',
     },
     { name  => 'Percent Wrong Plot',
       value => 'plot per wrong',
       description => 'Generate a plot showing the percent of students who '.
           'were unable to complete each problem part',
       mode => 'plot',
       show => 'per wrong',
     },
     );

sub OutputDescriptions {
    my $Str = '';
    $Str .= "<h2>Output Modes</h2>\n";
    $Str .= "<dl>\n";
    foreach my $outputmode (@OutputOptions) {
	$Str .="    <dt>".$outputmode->{'name'}."</dt>\n";
	$Str .="        <dd>".$outputmode->{'description'}."</dd>\n";
    }
    $Str .= "</dl>\n";
    return $Str;
}

sub CreateAndParseOutputSelector {
    my $Str = '';
    my $elementname = 'outputmode';
    #
    # Format for output options is 'mode, restrictions';
    my $selected = 'html, with links';
    if (exists($ENV{'form.'.$elementname})) {
        if (ref($ENV{'form.'.$elementname} eq 'ARRAY')) {
            $selected = $ENV{'form.'.$elementname}->[0];
        } else {
            $selected = $ENV{'form.'.$elementname};
        }
    }
    #
    # Set package variables describing output mode
    $output_mode = 'html';
    $show        = 'all';
    foreach my $option (@OutputOptions) {
        next if ($option->{'value'} ne $selected);
        $output_mode = $option->{'mode'};
        $show        = $option->{'show'};
    }
    #
    # Build the form element
    $Str = qq/<select size="5" name="$elementname">/;
    foreach my $option (@OutputOptions) {
        $Str .= "\n".'    <option value="'.$option->{'value'}.'"';
        $Str .= " selected " if ($option->{'value'} eq $selected);
        $Str .= ">".$option->{'name'}."<\/option>";
    }
    $Str .= "\n</select>";
    return $Str;
}

###############################################
###############################################

###############################################
###############################################
sub Gather_Student_Data {
    my ($r) = @_;
    my $c = $r->connection();
    #
    my @Sequences = &Apache::lonstatistics::Sequences_with_Assess();
    #
    my @Students = @Apache::lonstatistics::Students;
    #
    # Open the progress window
    my %prog_state=&Apache::lonhtmlcommon::Create_PrgWin
        ($r,'Statistics Compilation Status',
         'Statistics Compilation Progress', scalar(@Students));
    #
    while (my $student = shift @Students) {
        return if ($c->aborted());
        my ($status,undef) = &Apache::loncoursedata::ensure_current_data
            ($student->{'username'},$student->{'domain'},
             $ENV{'request.course.id'});
        &Apache::lonhtmlcommon::Increment_PrgWin($r,\%prog_state,
                                                 'last student');
    }
    &Apache::lonhtmlcommon::Close_PrgWin($r,\%prog_state);
    $r->rflush();
}

###############################################
###############################################

###############################################
###############################################
sub BuildProblemStatisticsPage {
    my ($r,$c)=@_;
    #
    $output_mode = 'html';
    $show = 'grouped';
    #
    $r->print(&CreateInterface());
    $r->print('<input type="hidden" name="statsfirstcall" value="no" />');
    $r->print('<input type="hidden" name="sortby" value="'.$ENV{'form.sortby'}.
              '" />');
    if (! exists($ENV{'form.statsfirstcall'})) {
        return;
    }
    #
    &Gather_Student_Data($r);
    #
    #
    if ($output_mode eq 'html') {
        $r->print("<h2>".
                  $ENV{'course.'.$ENV{'request.course.id'}.'.description'}.
                  "</h2>\n");
        $r->print("<h3>".localtime(time)."</h3>");
        $r->rflush();
        if ($show eq 'grouped') {
            &output_html_grouped_by_sequence($r);
        } elsif ($show eq 'ungrouped') {
            &output_html_ungrouped($r);
        }
    } else {
        $r->print("<h1>Not implemented</h1>");
    }
    return;
}

sub output_html_grouped_by_sequence {
    my ($r) = @_;
    #$r->print(&ProblemStatisticsLegend());
    my @Header = ("Title","Part","#Stdnts","Tries","Mod",
                  "Mean","#YES","#yes","%Wrng","DoDiff",
                  "S.D.","Skew.");#,"D.F.1st","D.F.2nd");
    # #FFFFE6 #EEFFCC #DDFFFF FFDDDD #DDFFDD #FFDDFF
    foreach my $sequence (&Apache::lonstatistics::Sequences_with_Assess()) {
        next if ($sequence->{'num_assess'}<1);
        $r->print("<h3>".$sequence->{'title'}."</h3>");
        $r->print('<table border="0"><tr><td bgcolor="#777777">'."\n");
        $r->print('<table border="0" cellpadding="3">'."\n");
        $r->print('<tr bgcolor="#FFFFE6"><th>'.
                  join("</th><th>",@Header)."</th></tr>\n");
        foreach my $resource (@{$sequence->{'contents'}}) {
            next if ($resource->{'type'} ne 'assessment');
            foreach my $part (@{$resource->{'parts'}}) {
                if ($part == 0) {
                    $part = '&nbsp;';
                }
                my ($num,$tries,$mod,$mean,$Solved,$solved,$DegOfDiff,$STD,
                    $SKEW) = &Apache::loncoursedata::get_problem_statistics
                        (undef,$resource->{'symb'},$part,
                         $ENV{'request.course.id'});
                my $wrongpercent = 0;
                if (defined($num) && $num > 0) {
                    $wrongpercent=int(10*100*($num-$Solved+$solved)/$num)/10;
                }
                $r->print('<tr>'.&statistics_html_table_data
                          ($resource,$part,$num,$tries,$mod,$mean,$Solved,
                           $solved,$wrongpercent,$DegOfDiff,$STD,$SKEW).
                          "</tr>\n");
            }
        }
        $r->print("</table>\n");
        $r->print("</td></tr></table>\n");
        $r->rflush();
    }
    #
    return;
}


###############################################
###############################################

###############################################
###############################################
sub output_html_ungrouped {
    my ($r) = @_;
    #
    my $show_container = 0;
    #$r->print(&ProblemStatisticsLegend());
    my @Header = ("Title","Part","#Stdnts","Tries","Mod",
                  "Mean","#YES","#yes","%Wrng","DoDiff",
                  "S.D.","Skew.");#,"D.F.1st","D.F.2nd");
    #
    my $sortby = undef;
    foreach (@Header) {
        if ($ENV{'form.sortby'} eq $_) {
            $sortby = $_;
        }
    }
    if (! defined($sortby) || $sortby eq '') {
        $sortby = 'Container';
    }
    # #FFFFE6 #EEFFCC #DDFFFF FFDDDD #DDFFDD #FFDDFF
    my @Sequences = &Apache::lonstatistics::Sequences_with_Assess();
    if (@Sequences > 1) {
        unshift(@Header,"Container");
        $show_container = 1;
    }
    #
    $r->print('<table border="0"><tr><td bgcolor="#777777">'."\n");
    $r->print('<table border="0" cellpadding="3">'."\n");
    my $Str = '';
    foreach (@Header) {
        if (/^(Part)$/) {  # Do not allow sorting on this field
            $Str .= '<th>'.$_.'</th>';
        } else {
            $Str .= '<th>'.
     '<a href="javascript:document.Statistics.sortby.value='."'$_'".
         ';document.Statistics.submit();">'.
             $_.'</a></th>';
        }
    }
    $r->print('<tr bgcolor="#FFFFE6">'.$Str."</tr>\n");
    $r->rflush();
    #
    # Compile the data
    my %Statshash;
    my @Statsarray;
    foreach my $sequence (@Sequences) {
        next if ($sequence->{'num_assess'}<1);
        foreach my $resource (@{$sequence->{'contents'}}) {
            next if ($resource->{'type'} ne 'assessment');
            foreach my $part (@{$resource->{'parts'}}) {
                my ($num,$tries,$mod,$mean,$Solved,$solved,$DegOfDiff,$STD,
                    $SKEW) = &Apache::loncoursedata::get_problem_statistics
                        (undef,$resource->{'symb'},$part,
                         $ENV{'request.course.id'});
                my $wrongpercent = 0;
                if (defined($num) && $num > 0) {
                    $wrongpercent=int(10*100*($num-$Solved+$solved)/$num)/10;
                }
                my $key = $resource->{'symb'}.':'.$part;
                $Statshash{$key} = 
                    {
                        'sequence' => $sequence,
                        'resource' => $resource,
                        'Title' => $resource->{'title'},
                        'Part'  => $part,
                        '#Stdnts' => $num,
                        'Tries' => $tries,
                        'Mod' => $mod,
                        'Mean' => $mean,
                        '#YES' => $Solved,
                        '#yes' => $solved,
                        '%Wrng' => $wrongpercent,
                        'DoDiff' => $DegOfDiff,
                        'S.D.' => $STD,
                        'Skew' => $SKEW,
                    };
                push (@Statsarray,$Statshash{$key});
            }
        }
    }
    #
    # Sort the data
    if ($sortby eq 'Container') {
        foreach my $sequence (@Sequences) {
            next if ($sequence->{'num_assess'}<1);
            foreach my $resource (@{$sequence->{'contents'}}) {
                next if ($resource->{'type'} ne 'assessment');
                foreach my $part (@{$resource->{'parts'}}) {
                    my $key = $resource->{'symb'}.':'.$part;
                    $r->print('<tr>');
                    if ($show_container) {
                        $r->print('<td bgcolor="#FFFFE6">'
                                  .$sequence->{'title'}.'</td>');
                    }
                    $r->print(&stats_row_from_hash($Statshash{$key}));
                    $r->print("</tr>\n");
                }
            }
        }
    } else {
        # $sortby is already defined, so we can charge ahead
        my @OutputOrder;
        if ($sortby =~ /^(title|part)$/i) {
            # Alpha comparison
            @OutputOrder = sort {
                $b->{$sortby} cmp $a->{$sortby} ||
                    $b->{'Title'} cmp $a->{'Title'} ||
                        $b->{'Part'} cmp $a->{'Part'};
            } @Statsarray;
        } else {
            # Numerical comparison
            @OutputOrder = sort {
                my $retvalue = 0;
                if ($b->{$sortby} eq 'nan') {
                    if ($a->{$sortby} ne 'nan') {
                        $retvalue = -1;
                    } else {
                        $retvalue = 0;
                    }
                }
                if ($a->{$sortby} eq 'nan') {
                    if ($b->{$sortby} ne 'nan') {
                        $retvalue = 1;
                    }
                }
                if ($retvalue eq '0') {
                    $retvalue = $b->{$sortby} <=> $a->{$sortby} ||
                                $b->{'Title'} <=> $a->{'Title'} ||
                                $b->{'Part'}  <=> $a->{'Part'};
                }
                $retvalue;
            } @Statsarray;
        }
        foreach my $row (@OutputOrder) {
            $r->print('<tr>');
            if ($show_container) {
                $r->print('<td bgcolor="#FFFFE6">'
                          .$row->{'sequence'}->{'title'}.'</td>');
            }
            $r->print(&stats_row_from_hash($row));
            $r->print("</tr>\n");
        }
    }
    $r->print("</table>\n");
    $r->print("</td></tr></table>\n");
    $r->rflush();
    #
    return;
}

sub stats_row_from_hash {
    my ($data) = @_;
    if (ref($data) ne 'HASH') {
        my %Tmp = @_;
        $data = \%Tmp;
    }
    return &statistics_html_table_data($data->{'resource'},$data->{'Part'},
                                       $data->{'#Stdnts'}, $data->{'Tries'},
                                       $data->{'Mod'},     $data->{'Mean'},
                                       $data->{'#YES'},    $data->{'#yes'},
                                       $data->{"\%Wrng"},  $data->{'DoDiff'},
                                       $data->{'S.D.'},    $data->{'Skew'});
}

###############################################
###############################################

###############################################
###############################################
sub statistics_html_table_data {
    my ($resource,$part,$num,$tries,$mod,$mean,$Solved,$solved,$wrongpercent,
        $DegOfDiff,$STD,$SKEW) = @_;
    my $row = '';
    $row .= '<td bgcolor="#FFFFE6">'.
        '<a href="'.$resource->{'src'}.'" target="_blank" >'.
            $resource->{'title'}.'</a>'.
                '</td>';
    $row .= '<td bgcolor="#FFFFE6">'.$part.'</td>' if (defined($part));
    foreach ($num,$tries) {
        $row .= '<td bgcolor="#EEFFCC" align="right">'.$_.'</td>';
    }
    foreach ($mod,$mean) {
        $row .= '<td bgcolor="#DDFFFF" align="right">'.
                  sprintf("%5.2f",$_).'</td>';
    }
    foreach ($Solved,$solved) {
        $row .= '<td bgcolor="#DDFFFF" align="right">'.$_.'</td>';
    }
    foreach ($wrongpercent) {
        $row .= '<td bgcolor="#DDFFFF" align="right">'.
                  sprintf("%5.1f",$_).'</td>';
    }
    foreach ($DegOfDiff,$STD,$SKEW) {
        $row .= '<td bgcolor="#FFDDDD" align="right">'.
                  sprintf("%5.2f",$_).'</td>';
    }
    return $row;
}


###############################################
###############################################

sub BuildGraphicChart {
    my ($graph,$cacheDB,$courseDescription,$students,$courseID,$r,$c)=@_;
    my %cache;
    my $max;
    my $title = '';
    if($graph eq 'DoDiffGraph') {
	$title = 'Degree-of-Difficulty';
    } else {
	$title = 'Wrong-Percentage';
    }
    my $currentSequence = -1;
    my $sortProblems = 'Sort Within Sequence';
    my ($result, $orderedProblems) =
        &InitializeProblemStatistics($cacheDB, $students, $courseID, $c, $r);
    if($result ne 'OK') {
        return;
    }
    my @values = ();
    unless(tie(%cache,'GDBM_File',$cacheDB,&GDBM_READER(),0640)) {
        return 'Unable to tie database.7';
    }
    foreach(@$orderedProblems) {
        my ($sequence,$problem,$part)=split(':', $_);
        if($cache{'StatisticsMaps'} ne 'All Maps'  &&
           $cache{'StatisticsMaps'} ne $cache{$sequence.':title'}) {
             next;
        }
        if( $currentSequence == -1 ||
            ($sortProblems eq 'Sort Within Sequence' &&
            $currentSequence != $sequence)) {
	    if($currentSequence != -1) {
		&DrawGraph(\@values,$courseDescription,$title,$max,$r);
	    }
            if($sortProblems eq 'Sort Within Sequence') {
                $r->print('<br><b>'.$cache{$sequence.':title'}.'</b>'."\n");
            }
            $currentSequence = $sequence;
            @values = ();
	    $max=0;
        }
        my $data = 0;
        if($graph eq 'DoDiffGraph') {
            $data = sprintf("%.2f", $cache{$_.':degreeOfDifficulty'}),
        } else {
            $data = sprintf("%.1f", $cache{$_.':percentWrong'}),
        }
        if($max < $data) {
            $max = $data;
        }
        push(@values, $data);
    }
    untie(%cache);
    &DrawGraph(\@values,$courseDescription,$title,$max,$r);
    return;
}

sub DrawGraph {
    my ($values,$courseDescription,$title,$Max,$r)=@_;
    my $sendValues = join(',', @$values);
    my $sendCount = scalar(@$values);
    $r->print("<br>The Maximum Value is: $Max");
    if ( $Max > 1 ) {
	if ($Max % 10) {
            if ( int($Max) < $Max ) {
	    	$Max++;
		$Max = int($Max);
	    }
	}
    #(10 - $Max % 10);
    } else { $Max = 1; }
    my @GData = ('','Problem_number',$title,$Max,$sendCount,$sendValues);
#    $r->print('</form>'."\n");
    $r->print('<br>'."\n");
    $r->print('<IMG src="/cgi-bin/graph.png?'.
              (join('&', @GData)).'" border="1" />');
#    $r->print('<form>'."\n");
    $r->print('<br>'."\n");
}

#---- Problem Statistics Web Page ---------------------------------------
sub CreateProblemStatisticsTableHeading {
    my ($headings,$r)=@_;
    my $Str='';
    $Str .= '<tr>'."\n";
    $Str .= '<th bgcolor="#ffffe6">P#</th>'."\n";
    foreach(@$headings) {
	$Str .= '<th bgcolor="#ffffe6">';
        $Str .= '<a href="/adm/statistics?reportSelected=';
        $Str .= &Apache::lonnet::escape('Problem Statistics');
        $Str .= '&ProblemStatisticsSort=';
        $Str .= &Apache::lonnet::escape($_).'">'.$_.'</a>&nbsp</th>'."\n";
    }
    $Str .= "\n".'</tr>'."\n";
    return $Str;
}

sub BuildStatisticsTable {
    my ($cache,$displayFormat,$sortProblems,$orderedProblems,$headings,
        $r,$color)=@_;
    my $count = 1;
    my $currentSequence = -1;
    foreach(@$orderedProblems) {
        my ($sequence,$problem,$part)=split(':', $_);
        if($cache->{'StatisticsMaps'} ne 'All Maps'  &&
           $cache->{'StatisticsMaps'} ne $cache->{$sequence.':title'}) {
            next;
        }
        if($currentSequence == -1 ||
           ($sortProblems eq 'Sort Within Sequence' &&
            $currentSequence != $sequence)) {
            if($displayFormat ne 'Display CSV Format') {
                if($currentSequence ne -1) {
                    $r->print('</table>');
                    $r->print('</td></tr></table><br>');
                }
                if($sortProblems eq 'Sort Within Sequence') {
                    $r->print('<b>'.$cache->{$sequence.':title'}.'</b>');
                }
                $r->print('<table border="0"><tr><td bgcolor="#777777">'."\n");
                $r->print('<table border="0" cellpadding="3">'."\n");
                $r->print(&CreateProblemStatisticsTableHeading($headings, $r));
            } else {
                if($sortProblems eq 'Sort Within Sequence') {
                    $r->print('"'.$cache->{$sequence.':title'}.'"');
                }
                $r->print('<br>');
            }
            $currentSequence = $sequence;
        }
        my $ref = '<a href="'.$cache->{$problem.':source'}.
                  '" target="_blank">'.$cache->{$problem.':title'}.'</a>';
        my $title = $cache->{$problem.':title'};
        if($part != 0) {
            $title .= ' Part '.$part;
        }
        my $source = $cache->{$problem.':source'};
        my $tableData = join('&', $ref, $title, $source,
                       $cache->{$_.':studentCount'},
                       $cache->{$_.':totalTries'},
                       $cache->{$_.':maxTries'},
                       $cache->{$_.':mean'},
                       $cache->{$_.':correct'},
                       $cache->{$_.':correctByOverride'},
                       $cache->{$_.':percentWrong'},
                       $cache->{$_.':degreeOfDifficulty'},
                       $cache->{$_.':standardDeviation'},
                       $cache->{$_.':skewness'},
                       $cache->{$_.':discriminationFactor1'},
                       $cache->{$_.':discriminationFactor2'});
        &TableRow($displayFormat,$tableData,$count,$r,$color);
        $count++;
    }
    if($displayFormat ne 'Display CSV Format') {
        $r->print('</table>'."\n");
        $r->print('</td></tr></table>');
    } else {
        $r->print('<br>');
    }
    return;
}

sub TableRow {
    my ($displayFormat,$Str,$RealIdx,$r,$color)=@_;
    my($ref,$title,$source,$StdNo,$TotalTries,$MxTries,$Avg,$YES,$Override,
       $Wrng,$DoD,$SD,$Sk,$_D1,$_D2)=split(/\&/,$Str);	
    my $Ptr;
    if($displayFormat eq 'Display CSV Format') {
        $Ptr='"'.$RealIdx.'",'."\n".
             '"'.$title.'",'."\n".
             '"'.$source.'",'."\n".
             '"'.$StdNo.'",'."\n".
             '"'.$TotalTries.'",'."\n".
             '"'.$MxTries.'",'."\n".
             '"'.$Avg.'",'."\n".
             '"'.$YES.'",'."\n".
             '"'.$Override.'",'."\n".
             '"'.$Wrng.'",'."\n".
             '"'.$DoD.'",'."\n".
             '"'.$SD.'",'."\n".
             '"'.$Sk.'",'."\n".
             '"'.$_D1.'",'."\n".
             '"'.$_D2.'"'."\n".
             "<br>\n";
        $r->print("\n".$Ptr);
    } else {
        $Ptr='<tr>'."\n".
             '<td bgcolor="#ffffe6">'.$RealIdx.'</td>'."\n".
             '<td bgcolor="#ffffe6">'.$ref.'</td>'."\n".
             '<td bgcolor='.$color->{"yellow"}.'> '.$StdNo.'</td>'."\n".
             '<td bgcolor='.$color->{"yellow"}.'>'.$TotalTries.'</td>'."\n".
             '<td bgcolor='.$color->{"yellow"}.'>'.$MxTries.'</td>'."\n".
             '<td bgcolor='.$color->{"gb"}.'>'.$Avg.'</td>'."\n".
             '<td bgcolor='.$color->{"gb"}.'> '.$YES.'</td>'."\n".
             '<td bgcolor='.$color->{"gb"}.'> '.$Override.'</td>'."\n".
             '<td bgcolor='.$color->{"red"}.'> '.$Wrng.'</td>'."\n".
             '<td bgcolor='.$color->{"red"}.'> '.$DoD.'</td>'."\n".
             '<td bgcolor='.$color->{"green"}.'> '.$SD.'</td>'."\n".
             '<td bgcolor='.$color->{"green"}.'> '.$Sk.'</td>'."\n".
             '<td bgcolor='.$color->{"purple"}.'> '.$_D1.'</td>'."\n".
	     '<td bgcolor='.$color->{"purple"}.'> '.$_D2.'</td>'."\n";
        $r->print($Ptr.'</tr>'."\n");
    }
    return;
}

# For loading the colored table for display or un-colored for print
sub setbgcolor {
    my $PrintTable=shift;
    my %color;
    if ($PrintTable){
	$color{"gb"}="#FFFFFF";
	$color{"red"}="#FFFFFF";
	$color{"yellow"}="#FFFFFF";
	$color{"green"}="#FFFFFF";
	$color{"purple"}="#FFFFFF";
    } else {
	$color{"gb"}="#DDFFFF";
	$color{"red"}="#FFDDDD";
	$color{"yellow"}="#EEFFCC";
	$color{"green"}="#DDFFDD";
	$color{"purple"}="#FFDDFF";
    }
    return \%color;
}

sub ProblemStatisticsButtons {
    my ($displayFormat, $displayLegend, $sortProblems)=@_;
    my $Ptr = '<tr><td></td><td align="left">';
    $Ptr .= '<input type="submit" name="DoDiffGraph" ';
    $Ptr .= 'value="Plot Degree of Difficulty" />'."\n";
    $Ptr .= '</td><td align="left">';
    $Ptr .= '<input type="submit" name="PercentWrongGraph" ';
    $Ptr .= 'value="Plot Percent Wrong" />'."\n";
    $Ptr .= '</td></tr><tr><td></td><td>'."\n";
    $Ptr .= '<input type="submit" name="SortProblems" ';
    if($sortProblems eq 'Sort All Problems') {
        $Ptr .= 'value="Sort Within Sequence" />'."\n";
    } else {
        $Ptr .= 'value="Sort All Problems" />'."\n";
    }
    $Ptr .= '</td><td align="left">';
    $Ptr .= '<input type="submit" name="DisplayLegend" ';
    if($displayLegend eq 'Show Legend') {
        $Ptr .= 'value="Hide Legend" />'."\n";
    } else {
        $Ptr .= 'value="Show Legend" />'."\n";
    }
    $Ptr .= '</td><td align="left">';
    $Ptr .= '<input type="submit" name="DisplayCSVFormat" ';
    if($displayFormat eq 'Display CSV Format') {
        $Ptr .= 'value="Display Table Format" />'."\n";
    } else {
        $Ptr .= 'value="Display CSV Format" />'."\n";
    }
    $Ptr .= '</td></tr>';
    return $Ptr;
}

sub ProblemStatisticsLegend {
    my $Ptr = '';
    $Ptr = '<table border="0">';
    $Ptr .= '<tr><td>';
    $Ptr .= '<b>#Stdnts</b></td>';
    $Ptr .= '<td>Total number of students attempted the problem.';
    $Ptr .= '</td></tr><tr><td>';
    $Ptr .= '<b>Tries</b></td>';
    $Ptr .= '<td>Total number of tries for solving the problem.';
    $Ptr .= '</td></tr><tr><td>';
    $Ptr .= '<b>Mod</b></td>';
    $Ptr .= '<td>Largest number of tries for solving the problem by a student.';
    $Ptr .= '</td></tr><tr><td>';
    $Ptr .= '<b>Mean</b></td>';
    $Ptr .= '<td>Average number of tries. [ Tries / #Stdnts ]';
    $Ptr .= '</td></tr><tr><td>';
    $Ptr .= '<b>#YES</b></td>';
    $Ptr .= '<td>Number of students solved the problem correctly.';
    $Ptr .= '</td></tr><tr><td>';
    $Ptr .= '<b>#yes</b></td>';
    $Ptr .= '<td>Number of students solved the problem by override.';
    $Ptr .= '</td></tr><tr><td>';
    $Ptr .= '<b>%Wrong</b></td>';
    $Ptr .= '<td>Percentage of students who tried to solve the problem ';
    $Ptr .= 'but is still incorrect. [ 100*((#Stdnts-(#YES+#yes))/#Stdnts) ]';
    $Ptr .= '</td></tr><tr><td>';
    $Ptr .= '<b>DoDiff</b></td>';
    $Ptr .= '<td>Degree of Difficulty of the problem.  ';
    $Ptr .= '[ 1 - ((#YES+#yes) / Tries) ]';
    $Ptr .= '</td></tr><tr><td>';
    $Ptr .= '<b>S.D.</b></td>';
    $Ptr .= '<td>Standard Deviation of the tries.  ';
    $Ptr .= '[ sqrt(sum((Xi - Mean)^2)) / (#Stdnts-1) ';
    $Ptr .= 'where Xi denotes every student\'s tries ]';
    $Ptr .= '</td></tr><tr><td>';
    $Ptr .= '<b>Skew.</b></td>';
    $Ptr .= '<td>Skewness of the students tries.';
    $Ptr .= '[(sqrt( sum((Xi - Mean)^3) / #Stdnts)) / (S.D.^3)]';
    $Ptr .= '</td></tr><tr><td>';
    $Ptr .= '<b>Dis.F.</b></td>';
    $Ptr .= '<td>Discrimination Factor: A Standard for evaluating the ';
    $Ptr .= 'problem according to a Criterion<br>';
    $Ptr .= '<b>[Criterion to group students into %27 Upper Students - ';
    $Ptr .= 'and %27 Lower Students]</b><br>';
    $Ptr .= '<b>1st Criterion</b> for Sorting the Students: ';
    $Ptr .= '<b>Sum of Partial Credit Awarded / Total Number of Tries</b><br>';
    $Ptr .= '<b>2nd Criterion</b> for Sorting the Students: ';
    $Ptr .= '<b>Total number of Correct Answers / Total Number of Tries</b>';
    $Ptr .= '</td></tr>';
    $Ptr .= '<tr><td><b>Disc.</b></td>';
    $Ptr .= '<td>Number of Students had at least one discussion.';
    $Ptr .= '</td></tr></table>';
    return $Ptr;
}

#---- END Problem Statistics Web Page ----------------------------------------

1;
__END__