Plotting points on a HSV color wheel

Question

I am using the following code:

import numpy as np
from matplotlib import cm
import matplotlib as mpl

fig = plt.figure()

display_axes = fig.add_axes([0.1,0.1,0.8,0.8], projection='polar')
display_axes._direction = 2*np.pi ## This is a nasty hack - using the hidden field to 
                                  ## multiply the values such that 1 become 2*pi
                                  ## this field is supposed to take values 1 or -1 only!!

norm = mpl.colors.Normalize(0.0, 2*np.pi)

# Plot the colorbar onto the polar axis
# note - use orientation horizontal so that the gradient goes around
# the wheel rather than centre out
quant_steps = 2056
cb = mpl.colorbar.ColorbarBase(display_axes, cmap=cm.get_cmap('hsv',quant_steps),
                                   norm=norm,
                                   orientation='horizontal')

# aesthetics - get rid of border and axis labels                                   
cb.outline.set_visible(False)                                 
display_axes.set_axis_off()
plt.show() # Replace with plt.savefig if you want to save a file

from Plot a (polar) color wheel based on a colormap using Python/Matplotlib here.

I need to plot black points on this color wheel. How could I do this? Is it possible to overlay a scatter plot on top of this color wheel?

Answer 1

You don't need to do anything special, just plot a scatter plot. The domain is set to be 0 to 2pi for theta and 0 to 1 for r.

# your code above, minus the plt.show()

theta = np.random.uniform(0, 2*np.pi, 20)
r = np.random.uniform(0, 1, 20)
plt.scatter(theta, r, color="k", marker="x")
plt.show()