--- loncom/homework/templates/Rnumerical.problem	2009/04/18 23:43:54	1.1
+++ loncom/homework/templates/Rnumerical.problem	2009/06/23 03:01:20	1.2
@@ -5,20 +5,21 @@ $n=&random(15,25,1);
 $offset=&random(2,5,0.1);
 $slope=&random(0.6,2.5,0.1);
 # construct a data set using R
-$data=&cas('R',"set.seed($seed);x<-1:$n;w<-1+sqrt(x)/2;data.frame(x=x,y=$offset+$slope*x+rnorm(x)*w);");
-# separate into an x and a y vector
-@datatable=split(/\s+/gs,$data);
-for ($i=0;$i<2*$n;$i+=2) {
-    push(@x,$datatable[$i]);
-    push(@y,$datatable[$i+1]);
-}
+# dump is for debugging, print to screen to see data structure
+($data,$dump)=&cas_hashref('R',"set.seed($seed);x<-1:$n;w<-1+sqrt(x)/2;data.frame(x=x,y=$offset+$slope*x+rnorm(x)*w);");
+@x=&cas_hashref_array($data,'x');
+@y=&cas_hashref_array($data,'y');
 $datax=join(',',@x);
 $datay=join(',',@y);
 # calculate the right answer using R
-($intercept,$slope)=split(/\s+/,&cas('R',"x<-c($datax);y<-c($datay);dataset<-data.frame(x=x,y=y);fm<-lm(y~x,data=dataset);array(coef(fm),dim=2);"));
-$answer="$slope*x+$intercept";
+($answerdata,$dump)=&cas_hashref('R',"x<-c($datax);y<-c($datay);dataset<-data.frame(x=x,y=y);fm<-lm(y~x,data=dataset);");
+$answer=&cas_hashref_entry($answerdata,'coefficients','x').'*x+'.&cas_hashref_entry($answerdata,'coefficients','(Intercept)');
 </script>
-<gnuplot width="400" solid="0" plotcolor="monochrome" gridlayer="off" bmargin="default" font="9" alttag="dynamically generated plot" bgcolor="xffffff" texfont="22" transparent="off" plottype="Cartesian" rmargin="default" gridtype="Cartesian" minor_ticscale="0.5" fontface="sans-serif" grid="on" align="right" texwidth="93" height="300" border="on" samples="100" fgcolor="x000000" major_ticscale="1" tmargin="default" lmargin="default" fillstyle="empty">
+
+<startouttext />
+Consider the plotted data set.<br />
+<endouttext />
+<gnuplot width="400" solid="0" plotcolor="monochrome" gridlayer="off" bmargin="default" font="9" alttag="dynamically generated plot" bgcolor="xffffff" texfont="22" transparent="off" plottype="Cartesian" rmargin="default" gridtype="Cartesian" minor_ticscale="0.5" fontface="sans-serif" grid="on" align="left" texwidth="93" height="300" border="on" samples="100" fgcolor="x000000" major_ticscale="1" tmargin="default" lmargin="default" fillstyle="empty">
     <curve linestyle="points" linetype="solid" color="x000000" pointtype="3" limit="closed" pointsize="2" linewidth="1">
         <data>@x</data>
         <data>@y</data>
@@ -27,13 +28,11 @@ $answer="$slope*x+$intercept";
 </gnuplot>
 
 <startouttext />
-Consider the data set
-<pre>$data</pre>
-
+<br />
 Give a linear function approximating the data.<br />
 <tt>y(x)=</tt>
 <endouttext />
-<formularesponse answer="$answer" samples="x@1:$n#20">
+<formularesponse id="11" answer="$answer" samples="x@1:$n#20">
     <responseparam name="tol" default="2%" description="Numerical Tolerance" type="tolerance" />
     <textline size="25" readonly="no" />