There are four possible sets of axes available; the keyword 4#4axes5#5 is used to
select the axes for which a particular line should be scaled. x1y1 refers
to the axes on the bottom and left; x2y2 to those on the top and right;
x1y2 to those on the bottom and right; and x2y1 to those on the top and
left. Ranges specified on the plot command apply only to the first set of
axes (bottom left).
