How do I use one colormap to filter data on another colormap?

I have two colormaps which are both created using arrays of (n,n) size (n being an even integer).

The first represents the intensity of a light beam on a surface. Intensity across the surface

The other represents the polarization of the beam across the same surface, at the same time. Polarization of the beam across the surface in °

I would like to only show values of the second colormap where there is a certain amount of intensity.

It would be even better if the gradient of the first colormap could be applied over the second colormap.

Solution

You can create a mask array of 0 and 1, with the same dimensions and size as the image and set the values of this mask to 1 where the intensity is above your threshold, then multiply the polarisation by this mask.

Let's say you have the two arrays intensity and polarisation. The mask array will be 0 except where intensity is above the threshold.

import numpy as np

intensity = np.ones((50,50)) * np.random.rand(50,50)
polarisation = np.ones((50,50))
threshold = 0.5

mask = np.zeros(np.shape(intensity))

mask[np.where(intensity>threshold)] = 1

filtered_polarisation = polarisation * mask