--- loncom/homework/templates/Plot_data.problem	2007/07/30 21:52:21	1.3
+++ loncom/homework/templates/Plot_data.problem	2010/08/01 14:15:12	1.6
@@ -1,35 +1,39 @@
 <problem>
 
 <script type="loncapa/perl">
-# Enter computations here
-### $amplitude = &random(1,4,0.5);
-### $x_min = -5;
-### $x_max =  5;
-### for ($x=$x_min;$x<=$x_max;$x=$x+0.05) {
-###     push(@X,$x);
-###     push(@Y,$amplitude*sin($x));
-### }
+#
+# This example populates arrays with the x and y coordinates of the plot.
+# For continuous functions, another approach is to use curve plots.
+#
+$amplitude = &random(1,4,0.5);
+$x_min = -5;
+$x_max =  5;
+for ($x=$x_min;$x<=$x_max;$x=$x+0.05) {
+   push(@X,$x);
+   push(@Y,$amplitude*sin($x));
+# Safeguard:
+# The following line limits the size of the array to 1000 to avoid infinite loops
+   if (($#X>1000) || ($#Y>1000)) { last; }
+}
 </script>
 
 <gnuplot width="300" transparent="off" samples="100" grid="on" font="9" bgcolor="xffffff" height="300" align="left" fgcolor="x000000" border="on" plottype="Cartesian" >
-    <axis xmin="0" ymin="0" xmax="10" ymax="10" color="x000000" />
+    <axis xmin="$x_min" ymin="-5" xmax="$x_max" ymax="5" color="x000000" />
     <xlabel>Label X</xlabel>
     <ylabel>Label Y</ylabel>
     <curve linestyle="linespoints" name="My Plot" pointtype="0" color="x000000">
-        <data>1,2,3,4,5,6,7,8,9</data>
-        <data>1,2,3,4,5,6,7,8,9</data>
+        <data>@X</data>
+        <data>@Y</data>
     </curve>
 </gnuplot>
 
-<startouttext />Enter Question Text Here.<endouttext />
+<startouttext />
+What is the amplitude of this function?
+<endouttext />
 
-<numericalresponse answer="">
+<numericalresponse answer="$amplitude" format="2s">
     <responseparam name="tol" type="tolerance" description="Numerical Tolerance" default="5%" />
-    <responseparam name="sig" type="int_range,0-16" description="Significant Figures" default="0,15" />
-    <textline />
-<hintgroup>
-<startouttext /><endouttext />
-</hintgroup>
+    <textline readonly="no" />
 </numericalresponse>
-</problem>
 
+</problem>