Generate the plot. Both HTML= and HTML_LEGEND= specify CITYDRILL as the variable that contains the targets for the drill-down links. HTML= determines that each plot point will be a hot zone that links to target output, and HTML_LEGEND= determines that the legend symbols will be hot zones that link to target output. This GPLOT procedure generates the first piece of output in this program; thus, the plot receives the first default anchor name, which is IDX. 
proc gplot data=newtemp;
   plot fahrenheit*month=city / hminor=0
        html=citydrill
        html_legend=citydrill;
run;
quit;