xytitles, xtitle, ytitle
-or- xytitles, xtitle, ytitle, [deltax,deltay]
Plot XTITLE horizontally under the viewport and YTITLE vertically
to the left of the viewport. If the tick numbers interfere with
the labels, you can specify the [DELTAX,DELTAY] in NDC units to
displace the labels. (Especially for the y title, the adjustment
may depend on how many digits the numbers on your scale actually
have.) Note that DELTAX moves YTITLE and DELTAY moves XTITLE.
WARNING: There is no easy way to ensure that this type of title
will not interfere with the tick numbering. Interference
may make the numbers or the title or both illegible.
interpreted function, defined at i0/graph.i line 625