--- loncom/xml/lonplot.pm	2001/12/28 19:04:56	1.22
+++ loncom/xml/lonplot.pm	2001/12/28 19:40:47	1.23
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # Dynamic plot
 #
-# $Id: lonplot.pm,v 1.22 2001/12/28 19:04:56 matthew Exp $
+# $Id: lonplot.pm,v 1.23 2001/12/28 19:40:47 matthew Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -263,7 +263,7 @@ my %curve_defaults =
 my (%plot,%key,%axis,$title,$xlabel,$ylabel,@labels,@curves);
 
 sub start_plot {
-    %plot    = undef;   %key     = undef;   %axis   = undef; 
+    %plot    = ();      %key     = ();      %axis   = (); 
     $title   = undef;   $xlabel  = undef;   $ylabel = undef;
     $#labels = -1;      $#curves = -1;
     #
@@ -716,12 +716,12 @@ sub write_gnuplot_file {
     $gnuplot_input .= "set title  \"$title\"\n"  if (defined($title)) ;
     $gnuplot_input .= "set xlabel \"$xlabel\"\n" if (defined($xlabel));
     $gnuplot_input .= "set ylabel \"$ylabel\"\n" if (defined($ylabel));
-    if (defined(%axis)) {
+    if (%axis) {
 	$gnuplot_input .= "set xrange \[$axis{'xmin'}:$axis{'xmax'}\]\n";
 	$gnuplot_input .= "set yrange \[$axis{'ymin'}:$axis{'ymax'}\]\n";
     }
     # Key
-    if (defined(%key)) {
+    if (%key) {
 	$gnuplot_input .= 'set key '.$key{'pos'}.' ';
 	if ($key{'title'} ne '') {
 	    $gnuplot_input .= 'title "'.$key{'title'}.'" ';
@@ -771,9 +771,9 @@ sub write_gnuplot_file {
 sub check_inputs {
     ## Note: no inputs, no outputs - this acts only on global variables.
     ## Make sure we have all the input we need:
-    if (! defined(%plot  )) { &set_defaults(\%plot,\%plot_defaults); }
-    if (! defined(%key   )) {} # No key for this plot, thats okay
-    if (! defined(%axis  )) { &set_defaults(\%axis,\%axis_defaults); }
+    if (! %plot) { &set_defaults(\%plot,\%plot_defaults); }
+    if (! %key ) {} # No key for this plot, thats okay
+    if (! %axis) { &set_defaults(\%axis,\%axis_defaults); }
     if (! defined($title )) {} # No title for this plot, thats okay
     if (! defined($xlabel)) {} # No xlabel for this plot, thats okay
     if (! defined($ylabel)) {} # No ylabel for this plot, thats okay