Perform stepwise interpolation between points. If
y define a a series of points, a new point in inserted between each. Between
(x[i], y[i]) and
(x[i+1], y[i+1]), either
(x[i+1], y[i]) or
(x[i], y[i+1]) is inserted, depending on the
x: Point x-coordinate.
y: Point y-coordinate.
:hvfor horizontal then vertical, or
:vhfor vertical then horizontal.
plot(x=rand(25), y=rand(25), Stat.step, Geom.line)