I often find myself with a rectangular array of plots (e.g., 3 rows
and 4 columns), where I want to label each row and each column, but
without repeating labels across every subplot. A good approach is
to put the labels in the outer margin. This allows one to eliminate
redundant white space around the subplots. You can do this using mtext().
For example to put labels above each column:
> mtext('Winter',at=.15,side=3,outer=T,cex=1.2)
> mtext('Spring',at=.35,side=3,outer=T,cex=1.2)
> mtext('Summer',at=.65,side=3,outer=T,cex=1.2)
> mtext('Fall',at=.85,side=3,outer=T,cex=1.2)
Keywords: R, plotting, outer margin, labels, multiple panels
Created: 1/20/12.