--- loncom/homework/functionplotresponse.pm	2010/10/31 12:33:02	1.21
+++ loncom/homework/functionplotresponse.pm	2010/11/01 00:04:09	1.22
@@ -1,7 +1,7 @@
 # LearningOnline Network with CAPA
 # option list style responses
 #
-# $Id: functionplotresponse.pm,v 1.21 2010/10/31 12:33:02 www Exp $
+# $Id: functionplotresponse.pm,v 1.22 2010/11/01 00:04:09 www Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -524,7 +524,6 @@ sub indices_scale {
    my ($xmin,$xmax,$x)=@_;
    my $i=&array_index($xmin,$xmax,$x);
    my $xr=&index_x($xmin,$xmax,$i);
-   &Apache::lonnet::logthis("x:$x i:$i xr:$xr");
    if ($xr<$x) {
 # Desired x is right of array index
       if ($i>=200) { return (200,200,0); }
@@ -553,9 +552,37 @@ sub func_val {
    unless (defined($fl) || defined($fh)) { return undef; }
    unless (defined($fl)) { return $fh; }
    unless (defined($fh)) { return $fl; }
-   my $func=$fl+$factor*($fh-$fl);
-   &Apache::lonnet::logthis("x:$x func:$func factor:$factor il:$il ih:$ih fil:$fl fih:$fh");
-   return $func;
+   return $fl+$factor*($fh-$fl);
+}
+
+#
+# First derivative
+#
+
+sub dfuncdx_val {
+   my ($xmin,$xmax,$x)=@_;
+   my ($il,$ih,$factor)=&indices_scale($xmin,$xmax,$x);
+   my $fl=$Apache::functionplotresponse::dfuncdx[$il];
+   my $fh=$Apache::functionplotresponse::dfuncdx[$ih];
+   unless (defined($fl) || defined($fh)) { return undef; }
+   unless (defined($fl)) { return $fh; }
+   unless (defined($fh)) { return $fl; }
+   return $fl+$factor*($fh-$fl);
+}
+
+#
+# Second derivative
+#
+
+sub d2funcdx2_val {
+   my ($xmin,$xmax,$x)=@_;
+   my ($il,$ih,$factor)=&indices_scale($xmin,$xmax,$x);
+   my $fl=$Apache::functionplotresponse::d2funcdx2[$il];
+   my $fh=$Apache::functionplotresponse::d2funcdx2[$ih];
+   unless (defined($fl) || defined($fh)) { return undef; }
+   unless (defined($fl)) { return $fh; }
+   unless (defined($fh)) { return $fl; }
+   return $fl+$factor*($fh-$fl);
 }
 
 #
@@ -566,7 +593,7 @@ sub populate_arrays {
     my ($id,$xmin,$xmax)=@_;
     for (my $i=0; $i<=200; $i++) {
        $Apache::functionplotresponse::func[$i]=undef;
-       $Apache::functionplotresponse::dfunddx[$i]=undef;
+       $Apache::functionplotresponse::dfuncdx[$i]=undef;
        $Apache::functionplotresponse::d2funcd2x[$i]=undef;
     }
     unless ($xmax>$xmin) { return 'no_func'; }
@@ -591,7 +618,18 @@ sub populate_arrays {
                 if (($xi>$xiold) && ($xi>=0) && ($xi<=200)) {
                    if (defined($Apache::functionplotresponse::func[$xi])) { return 'no_func'; }
                    $xiold=$xi;
+# Function value
                    $Apache::functionplotresponse::func[$xi]=&cubic_hermite($t,@yparms);
+# dy/dx=dy/dt/(dx/dt)
+                   my $dxdt=&ddt_cubic_hermite($t,@xparms);
+                   if ($dxdt) {
+                      $Apache::functionplotresponse::dfuncdx[$xi]=&ddt_cubic_hermite($t,@yparms)/$dxdt;
+                   }
+# d^2y/dx^2
+                   my $d2xdt2=&d2dt2_cubic_hermite($t,@xparms);
+                   if ($d2xdt2) {
+                      $Apache::functionplotresponse::d2funcd2x[$xi]=&d2dt2_cubic_hermite($t,@yparms)/$d2xdt2;
+                   }
                 }
             }
         }
@@ -722,25 +760,6 @@ sub end_functionplotresponse {
         } else {
            $ad='INCORRECT';
         }
-        &func_val($xmin,$xmax,3.96);
-
-        &func_val($xmin,$xmax,3.965);
-
-        &func_val($xmin,$xmax,3.97);
-        &func_val($xmin,$xmax,3.975);
-        &func_val($xmin,$xmax,3.98);
-
-        &func_val($xmin,$xmax,3.985);
-        &func_val($xmin,$xmax,3.99);
-        &func_val($xmin,$xmax,3.995);
-
-        &func_val($xmin,$xmax,4);
-        &func_val($xmin,$xmax,4.05);
-        &func_val($xmin,$xmax,4.1);
-
-        &func_val($xmin,$xmax,4.15);
-        &func_val($xmin,$xmax,4.2);
-        &func_val($xmin,$xmax,4.25);
 
 #
 # Store grading info