addtxaxis

Adds a top x-axis with arbitrary scale

This function adds a second dummy x-axis on the top of a given axes object. This dummy x-axis has (internally) the same scaling (linear or log) than the main x-axis, but is used to display ticks and tick labels which are on a transformed scale.

The transformation is arbitrary, but the transformed axis cannot be used to create plots with transformed x coordinates. The given transformation is in fact the inverse transform, that is, the transform used to go from the secondary axis to the original axis (e.g. displaying a log scale would be done by providing a transform '10.^x').

The transformed axis can be removed cleanly by issuing a simple command.

Typical uses of addtxaxis would include displaying a secondary x-axis following reciprocal or logarithmic scales (e.g. frequency and wavelength on the same plot).