How to make the angles in a matplotlib polar plot go clockwise with 0° at the top?

Question

I am using matplotlib and numpy to make a polar plot. Here is some sample code:

import numpy as N import matplotlib.pyplot as P  angle = N.arange(0, 360, 10, dtype=float) * N.pi / 180.0 arbitrary_data = N.abs(N.sin(angle)) + 0.1 * (N.random.random_sample(size=angle.shape) - 0.5)  P.clf() P.polar(angle, arbitrary_data) P.show() 

You will notice that 0° is at 3 o'clock on the plot, and the angles go counterclockwise. It would be more useful for my data visualization purposes to have 0° at 12 o'clock and have the angles go clockwise. Is there any way to do this besides rotating the data and manually changing the axis labels?

Answer 1

Updating this question, in Matplotlib 1.1, there are now two methods in PolarAxes for setting the theta direction (CW/CCW) and location for theta=0.

Check out http://matplotlib.sourceforge.net/devel/add_new_projection.html#matplotlib.projections.polar.PolarAxes

Specifically, see set_theta_direction() and set_theta_offset().

Lots of people attempting to do compass-like plots it seems.

Answer 2

To expand klimaat's answer, with an example:

from math import radians import matplotlib.pyplot as plt  angle=[0.,5.,10.,15.,20.,25.,30.,35.,40.,45.,50.,55.,60.,65.,70.,75.,\        80.,85.,90.,95.,100.,105.,110.,115.,120.,125.]  angle = [radians(a) for a in angle]  lux=[12.67,12.97,12.49,14.58,12.46,12.59,11.26,10.71,17.74,25.95,\      15.07,7.43,6.30,6.39,7.70,9.19,11.30,13.30,14.07,15.92,14.70,\      10.70,6.27,2.69,1.29,0.81]  plt.clf() sp = plt.subplot(1, 1, 1, projection='polar') sp.set_theta_zero_location('N') sp.set_theta_direction(-1) plt.plot(angle, lux) plt.show() 

• matplotlib: Developer's guide for creating scales and transformations