Python 3.5 Matplotlib等高线图例

Question

Trying to add a legend to my contour plot:

Here is the relevant code part i am having problem with:

plt.figure()
CS = plt.contourf(gg, cc, zz_miss)
CS.clabel()
lbl = CS.cl_cvalues
plt.xlabel('gamma')
plt.ylabel('C = 1 / lambda')
plt.legend((lbl), loc= 'upper right')

plt.show()

The legend labels of the legend are correct, but why are the pertineent colors all smeared and out of place?

Answer 1

It's putting the literal polygons of your contour plot as they were markers. It's a problem.

I advise you to create a manual replacement for the color legend. Here is the modification you need to make into your code (generated synthetic data):

import matplotlib.pyplot as plt

plt.figure()
xx,yy = np.meshgrid(range(100),range(100))
gg = np.sqrt(xx*2+yy*2)
CS = plt.contourf(gg) #, cc, zz_miss)
proxy = [plt.Rectangle((0,0),1,1,fc = pc.get_facecolor()[0]) for pc in CS.collections]

plt.legend(proxy, [str(i) for i in range(8)])
plt.xlabel('gamma')
plt.ylabel('C = 1 / lambda')

plt.show()

, the result is this:

Answer 2

Thanks.
Also, found a slightly easier one: see result

CS = plt.contourf(gg, cc, zz_miss, alpha= 1)
nm, lbl = CS.legend_elements()
plt.legend(nm, lbl, title= 'MyTitle', fontsize= 8) 
plt.xlabel('gamma')
plt.ylabel('C = 1 / lambda')

here is the result: