--- loncom/homework/functionplotresponse.pm	2010/10/30 02:31:27	1.18
+++ loncom/homework/functionplotresponse.pm	2010/10/30 15:32:36	1.19
@@ -1,7 +1,7 @@
 # LearningOnline Network with CAPA
 # option list style responses
 #
-# $Id: functionplotresponse.pm,v 1.18 2010/10/30 02:31:27 www Exp $
+# $Id: functionplotresponse.pm,v 1.19 2010/10/30 15:32:36 www Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -514,16 +514,16 @@ sub array_index {
 sub populate_arrays {
     my ($id,$xmin,$xmax)=@_;
     for (my $i=0; $i<=200; $i++) {
-       undef $Apache::functionplotresponse::func[$i];
-       undef $Apache::functionplotresponse::dfunddx[$i];
-       undef $Apache::functionplotresponse::d2funcd2x[$i];
+       $Apache::functionplotresponse::func[$i]=undef;
+       $Apache::functionplotresponse::dfunddx[$i]=undef;
+       $Apache::functionplotresponse::d2funcd2x[$i]=undef;
     }
-    unless ($xmax>$xmin) { return; }
+    unless ($xmax>$xmin) { return 'no_func'; }
 # Run over all splines in response
     foreach my $label (split(/\,/,$env{"form.HWVAL_AllSplines_$id"})) {
+        my $xiold=-1;
 # Run over all points in spline
-        for (my $i=0; $i<$env{"form.HWVAL_SplineOrder_".$id."_".$label}; $i++) {
-            my $xiold=-1;
+        for (my $i=1; $i<$env{"form.HWVAL_SplineOrder_".$id."_".$label}; $i++) {
             my $ni=$i+1;
             my @xparms=($env{'form.HWVAL_'.$id.'_'.$label.'P'.$i.'_x'},
                         $env{'form.HWVAL_'.$id.'_'.$label.'S'.$i.'_x'},
@@ -533,12 +533,12 @@ sub populate_arrays {
                         $env{'form.HWVAL_'.$id.'_'.$label.'S'.$i.'_y'},
                         $env{'form.HWVAL_'.$id.'_'.$label.'P'.$ni.'_y'},
                         $env{'form.HWVAL_'.$id.'_'.$label.'S'.$ni.'_y'});
-
 # Run in small steps over spline parameter
             for (my $t=0; $t<=1; $t+=0.00025) {
                 my $xi=&array_index($xmin,$xmax,&cubic_hermite($t,@xparms));
-                if ($xi<$xiold-5) { return 'no_func'; }
-                if ($xi>$xiold) {
+                if ($xi<$xiold) { return 'no_func'; }
+                if (($xi>$xiold) && ($xi>=0) && ($xi<=200)) {
+                   if (defined($Apache::functionplotresponse::func[$xi])) { return 'no_func'; }
                    $xiold=$xi;
                    $Apache::functionplotresponse::func[$xi]=&cubic_hermite($t,@yparms);
                 }