GEN25 lets you create expon breakpoint functions, while GEN27 lets you
create linear breakpoint functions. Any chance we could have a GEN26
which is a mix between the two, thus allowing you to specify the type
of line drawn between points? Something like:

f # time size 26 x1 y1 s1 x2 y2 s2 x3 y3 s3  ...

x1, x2, x3, etc. -- locations in table at which to attain the
following y value. Must be in increasing order.

y1, y2, y3,, etc. -- Breakpoint values attained at the location
specified by the preceding x value.

s1, s2, s3, s4, s5, s6, etc. -- type of line between segments, 1 for
linear, 2 for exponential

Right now exponential and linear would do fine, but in the future it
could be extended to other types of curves too. It's something Peiman
and I discussed before, but neither of us ever got around to
requesting it :)