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