--- loncom/interface/statistics/lonproblemanalysis.pm	2005/04/07 06:56:24	1.120
+++ loncom/interface/statistics/lonproblemanalysis.pm	2006/02/04 19:06:53	1.124
@@ -1,6 +1,6 @@
 # The LearningOnline Network with CAPA
 #
-# $Id: lonproblemanalysis.pm,v 1.120 2005/04/07 06:56:24 albertel Exp $
+# $Id: lonproblemanalysis.pm,v 1.124 2006/02/04 19:06:53 bowersj2 Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -97,8 +97,11 @@ sub BuildProblemAnalysisPage {
             $r->print($html.(' 'x5));
         }
         #
-        $r->print(&Apache::lonstathelpers::submission_report_form
-                                                      ('problem_analysis'));
+
+        # This is commented out pending actual implementation of 
+        # CSV and Excel output.
+        #$r->print(&Apache::lonstathelpers::submission_report_form
+        #                                              ('problem_analysis'));
         #
         $r->print('<hr />');
         $r->rflush();
@@ -159,11 +162,14 @@ sub BuildProblemAnalysisPage {
         }
         $r->print('<hr />');
     } else {
-        $r->print('<input type="submit" name="ProblemAnalysis" value="'.
-                  &mt('Analyze Problem').'" />');
+        my $submit_button = '<input type="submit" '.
+            'name="ProblemAnalysis" value="'.
+            &mt('Analyze Problem').'" />';
+        $r->print($submit_button);
         $r->print('&nbsp;'x5);
         $r->print('<h3>'.&mt('Please select a problem to analyze').'</h3>');
-        $r->print(&Apache::lonstathelpers::problem_selector($problem_types));
+        $r->print(&Apache::lonstathelpers::problem_selector($problem_types,
+                                                            $submit_button));
     }
 }
 
@@ -338,7 +344,9 @@ sub numerical_plot_percent {
     while (my ($ans,$submissions) = each(%$responses)) {
         while (my ($submission,$counts) = each(%$submissions)) {
             my ($correct_count,$incorrect_count) = @$counts;
-            my $scaled_value = 100*($submission-$ans)/abs($ans);
+	    my $scaled_value = 
+		($ans) ? 100*($submission-$ans)/abs($ans)
+		       : 0;
             if ($scaled_value < $bins[0]) {
                 $bins[0]=$scaled_value -1;
             }
@@ -393,7 +401,8 @@ sub numerical_plot_differences {
     } elsif ($low_bin < 0 && $high_bin < -$low_bin) {
         $high_bin = -$low_bin;
     }
-    if (($high_bin -$low_bin)/$min_bin_size * 2 > $max_bins) {
+    if (!$min_bin_size ||
+        ($high_bin -$low_bin)/$min_bin_size * 2 > $max_bins) {
         $min_bin_size = abs($high_bin - $low_bin) / $max_bins * 2;
     }
     my @bins;