pythonmatplotlibplotresolution

polar plot with large number of points gets distorted

I want to plot a large number of data points on a polar scatter plot. I know how my data looks like from a cartesian plot, and I quickly noticed it got distorted on the polar plot. Now if I just plot the grid over which the data is plotted, it is already non-regular and distorted.

This is my code:

import numpy as np
import matplotlib.pyplot as plt

azimuths = np.linspace(0,2*np.pi,2000) # azimuthal angles
zeniths = np.linspace(0,100,200) # zenith is basically the radial extent of the plot
phi,r = np.meshgrid(azimuths,zeniths) # make the grid for the polar plot
fig, ax = plt.subplots(subplot_kw=dict(projection='polar'),figsize=(10,10)) # initialize figure
j=ax.scatter(phi,r,s=0.01) # make scatter plot
ax.set_rlim(0,100) # set radial limits

which yields the following figure: the distorted polar plot

I wonder if someone knows a way to create a uniform grid over the polar plot where no weird ripples appear, for this number of data points.

Solution

  • Increase the dpi parameter - the default is 100. Also consider increasing the figsize. The ripple effect is a display glitch, so this should fix things.

    fig, ax = plt.subplots(subplot_kw=dict(projection='polar'),figsize=(10,10), dpi=200)

    Check out the docs for this here.