How to create a polar contour plot
contourf, matplotlib, numpy, python
Solution
You should just be able to use `ax.contour` or `ax.contourf` with polar plots just as you normally would... You have a few bugs in your code, though. You convert things to radians, but then use the values in degrees when you plot. Also, you're passing in `r, theta` to contour when it expects `theta, r`.
As a quick example:
import numpy as np
import matplotlib.pyplot as plt
#-- Generate Data -----------------------------------------
# Using linspace so that the endpoint of 360 is included...
azimuths = np.radians(np.linspace(0, 360, 20))
zeniths = np.arange(0, 70, 10)
r, theta = np.meshgrid(zeniths, azimuths)
values = np.random.random((azimuths.size, zeniths.size))
#-- Plot... ------------------------------------------------
fig, ax = plt.subplots(subplot_kw=dict(projection='polar'))
ax.contourf(theta, r, values)
plt.show()
Problem
Update: I've done a full write-up of the way I found to do this on my blog at http://blog.rtwilson.com/producing-polar-contour-plots-with-matplotlib/ - you may want to check there first. I'm trying to plot a polar contour plot in matplotlib. I've found various resources on the internet, (a) I can't seem to get my code to work and (b) many of the resources appear rather old, and I'm wondering if there is a better way now. For example, http://www.mail-archive.com/matplotlib-users@lists.sourceforge.net/msg01953.html suggests that something may be done to improve things soon, and that was in 2006! I'd love to be able to plot proper polar contour plots - like pcolor lets you do for its type of plot (see commented out section below), but I can't seem to find any way to do that, so I'm converting to cartesian co-ordinates first. Anyway, I have the code that follows: ``` from pylab import * import numpy as np azimuths = np.arange(0, 360, 10) zeniths = np.arange(0, 70, 10) values = [] for azimuth in azimuths: for zenith in zeniths: print "%i %i" % (azimuth, zenith) # Run some sort of model and get some output # We'll just use rand for this example values.append(rand()) theta = np.radians(azimuths) values = np.array(values) values = values.reshape(len(zeniths), len(azimuths)) # This (from http://old.nabble.com/2D-polar-surface-plot-td28896848.html) # works fine ############## # Create a polar axes # ax = subplot(111, projection='polar') # pcolor plot onto it # c = ax.pcolor(theta, zeniths, values) # show() r, t = np.meshgrid(zeniths, azimuths) x = r*np.cos(t) y = r*np.sin(t) contour(x, y, values) ``` When I run that I get an error `TypeError: Inputs x and y must be 1D or 2D.`. I'm not sure why I get this, as both x and y are 2D. Am I doing something wrong? Also, it seems rather clunky to be putting my values returned from my model into a list and then reshaping it. Is there a better way to do this?