How to set limits around (on both sides of) 0, in a polar Matplotlib plot (wedge diagram)-CodePudding

I am making a wedge diagram (plotting quasars in space, with RA as theta and Dec as r). I need to set the limits of a polar plot on both sides of 0. My limits should go from 45 degrees to 315 degrees with 0 degrees in between those two values (45-0-315). How do I do this?

This is my code:

import numpy as np
import matplotlib.pyplot as plt

theta = (np.pi/180)*np.array([340.555906,3.592373,32.473440,33.171584,35.463857,44.268397,339.362504,345.211906,346.485567,346.811945,348.672405,349.180736,349.370850,353.098343])
r = np.array([-32.906663,-33.842402,-32.425917,-32.677975, -30.701083,-31.460307,-32.909861,-30.802969,-33.683759,-32.207783,-33.068686,-33.820102,-31.438195,-31.920375])

colors = 'red'

fig = plt.figure()
ax = fig.add_subplot(111, polar=True)
c = ax.scatter(theta, r, c=colors, cmap='hsv', alpha=0.75)

plt.show()

If I put the limits:

ax.set_thetamin(45)
ax.set_thetamax(-45)

I get the correct slice of the diagram, but the wrong values on the theta axis (the axis now goes from -45-45 degrees).

If I put the limits:

ax.set_thetamin(45)
ax.set_thetamax(315)

I get the wrong slice of the diagram, but the correct values on the theta axis.

What to do?

CodePudding user response：

It appears that matplotlib will only make the theta limits span across theta=0 if you have a positive and negative value for thetamin and thetamax. From the docstring for

For completeness, here I put it all together in your script:

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.ticker as ticker

theta = (np.pi/180)*np.array([340.555906,3.592373,32.473440,33.171584,35.463857,44.268397,339.362504,345.211906,346.485567,346.811945,348.672405,349.180736,349.370850,353.098343])
r = np.array([-32.906663,-33.842402,-32.425917,-32.677975, -30.701083,-31.460307,-32.909861,-30.802969,-33.683759,-32.207783,-33.068686,-33.820102,-31.438195,-31.920375])

colors = 'red'

fig = plt.figure()
ax = fig.add_subplot(111, polar=True)
c = ax.scatter(theta, r, c=colors, cmap='hsv', alpha=0.75)

ax.set_thetamin(45)
ax.set_thetamax(-45)

fmt = lambda x, pos: "{:g}".format(np.degrees(x if x >= 0 else x   2 * np.pi))
ax.xaxis.set_major_formatter(ticker.FuncFormatter(fmt))

plt.show()