Matplotlib 3.0 Cookbook

How to do it...

The following code block plots a polar graph and annotates a point on it:

1. Define the figure and axes on it, and declare the polar projection:

fig = plt.figure()ax = fig.add_subplot(111, projection='polar')

2. Define the data for the polar plot and plot it:

r = np.arange(0,1,0.001)theta = 2 * 2*np.pi * rax.plot(theta, r, color=[0.9,0.4,0.7], lw=3)

3. Plot a point with diamond marker at the 600 point on the polar curve:

ind = 600pointr, pointtheta = r[ind], theta[ind]ax.plot([pointtheta], [pointr], 'D', markersize=10)

4. Define the annotation for the diamond point and display the figure on the screen:

ax.annotate('a polar annotation',             xy=(pointtheta, pointr), xytext=(1.0, 0.75),              textcoords='figure  fraction', arrowprops=dict(facecolor='red', ...