Plotting Legend For 2d Numpy Array

I like to create a legend based on certain numbers using Numpy and Matplotlib but to no avail. So I started to play around with a test function to get it right before transferring

Solution 1:

Proxy artists

This can be done via proxy artists. Example from the docs:

import matplotlib.patchesas mpatches
import matplotlib.pyplotas plt

red_patch = mpatches.Patch(color='red', label='The red data')
plt.legend(handles=[red_patch])

plt.show()

But you need to figure out which colours correspond to which values. E.g.

cmap = plt.cm.viridismy_colors= {
    'Mineral 1' : 0.1,
    'Mineral 2' : 0.2,
    }

patches = [mpatches.Patch(color=cmap(v), label=k) for k,v in my_colors.items()]

plt.legend(handles=patches)

The numbers in the dictionary correspond to the data normalized to [0,1] and you need to plot your data with the same cmap, of course.

Alternative: Colorbar

Alternatively, you can add a colorbar (the equivalent to the legend in imshow plots and the like) and place your labels on the ticks.

cbar = plt.colorbar(cax, ticks=list(my_colors.values()), orientation='horizontal')
cbar.ax.set_xticklabels(list(my_colors.keys()))