I want to plot one data series against two axes. I can get the secondary axes
and I can get it onto the x axes at the top. What I want is to get the second
axes to be dependent on the first. You see the second axes is the volume
fraction of a composite ply and the first is the weight fraction. I want to
create a graph so that the data series I plot can be looked up by either the
volume fraction or the weight fraction. The problem is that the volume
fraction axes scale needs to be irregular since it's a nonlinear function of
the weight fraction. Firstly, I'd like to know if that's possible.

If so,
HOW DO I DO IT?