--- loncom/homework/functionplotresponse.pm	2010/11/07 12:28:28	1.27
+++ loncom/homework/functionplotresponse.pm	2010/11/07 21:10:14	1.29
@@ -1,7 +1,7 @@
 # LearningOnline Network with CAPA
 # option list style responses
 #
-# $Id: functionplotresponse.pm,v 1.27 2010/11/07 12:28:28 www Exp $
+# $Id: functionplotresponse.pm,v 1.29 2010/11/07 21:10:14 www Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -392,8 +392,34 @@ sub start_functionplotrule {
            &Apache::lonxml::get_param('value',$parstack,$safeeval)
           )));
    } elsif ($target eq 'edit') {
-      $result=&Apache::edit::tag_start($target,$token,'Function Plot Evaluation Rule').
-              &Apache::edit::end_row();
+        $result=&Apache::edit::tag_start($target,$token,'Function Plot Evaluation Rule').
+             &Apache::edit::text_arg('Index:','index',
+                                     $token,'4').' '.
+             &Apache::edit::select_arg(&mt('Function:'),'derivative',
+                                  [['0','Function itself'],
+                                   ['1','First derivative'],
+                                   ['2','Second derivative']],$token).
+             &Apache::edit::text_arg('(Initial) x-value:','xinitial',
+                                     $token,'4').' '.
+             &Apache::edit::text_arg('Final x-value for ranges:','xfinal',
+                                     $token,'4').' '.
+             &Apache::edit::select_arg(&mt('Relationship:'),'relationship',
+                                  [['eq','equal'],
+                                   ['ne','not equal'],
+                                   ['ge','greater than or equal'],
+                                   ['gt','greater than'],
+                                   ['lt','less than'],
+                                   ['le','less than or equal']],$token).
+             $result.= &Apache::edit::select_or_text_arg('Value:','value',
+                                               [['undef','not defined']],$token,'4').
+             &Apache::edit::text_arg('Percent error:','percenterror',
+                                     $token,'4').
+             &Apache::edit::end_row();
+  } elsif ($target eq 'modified') {
+    my $constructtag=&Apache::edit::get_new_args($token,$parstack,
+                                                 $safeeval,'index','derivative','xinitial','xfinal','relationship',
+                                                           'value','percenterror');
+    if ($constructtag) { $result=&Apache::edit::rebuild_tag($token); }
    }
    return $result;
 }
@@ -591,15 +617,19 @@ sub populate_arrays {
                    $xiold=$xi;
 # Function value
                    $Apache::functionplotresponse::func[$xi]=&cubic_hermite($t,@yparms);
+# Chain rule
 # 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
+# Faa di Bruno
+# d^2y/dx^2=(d^2y/dt^2)/(dx/dt)^2+(dy/dt)/(d^2x/dt^2)
                    my $d2xdt2=&d2dt2_cubic_hermite($t,@xparms);
-                   if ($d2xdt2) {
-                      $Apache::functionplotresponse::d2funcdx2[$xi]=&d2dt2_cubic_hermite($t,@yparms)/$d2xdt2;
+                   if (($dxdt) && ($d2xdt2)) {
+                      $Apache::functionplotresponse::d2funcdx2[$xi]=
+                         &d2dt2_cubic_hermite($t,@yparms)/($dxdt*$dxdt)
+                        +&ddt_cubic_hermite($t,@yparms)/$d2xdt2;
                    }
                 }
             }
@@ -788,9 +818,6 @@ sub functionplotrulecheck {
    for (my $i=$li; $i<=$lh; $i++) {
         my $val;
         if ($derivative==2) {
-            &Apache::lonnet::logthis("Second ".
-
-$Apache::functionplotresponse::d2funcdx2[$i-1].'__'.$Apache::functionplotresponse::d2funcdx2[$i].'__'.$Apache::functionplotresponse::d2funcdx2[$i+1]);
            $val=$Apache::functionplotresponse::d2funcdx2[$i];
         } elsif ($derivative==1) {
            $val=$Apache::functionplotresponse::dfuncdx[$i];