Matplotlib 3D绘图忽略不在圆圈中的值

Question

I am using matplotlib to plot a 3D 'histogram' with a wireframe of sine and cosine values of radiants of angles. The plot forms a circle as it should:

Now I am trying to just have the circle and its hills plotted but not the values in the circle and around. I have tried dismissing every value that is zero with

hist[hist==0] = np.nan

but then my plot looks like this, where also some values in the circle are zero and so the wireframe plot does not 'touch the ground' anymore.

So is there a way to dismiss the values in the circle and around it but that the plot still goes all the way down to zero?

This is my code:

from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as plt
import numpy as np

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')

cos, sin = np.genfromtxt('out_dhdrls_test0123.csv', delimiter=' ').transpose()

hist, xedges, yedges = np.histogram2d(cos, sin, bins=50, range=[[-1, 1], [-1, 1]])
hist[hist==0] = np.nan
xpos, ypos = np.meshgrid(xedges[:-1], yedges[:-1])
zpos = np.zeros_like(xpos)
ax.set_xlabel('xlabel')
ax.set_ylabel('ylabel')

ax.plot_wireframe(xpos, ypos, hist)
plt.show()

Answer 1

You might want to calculate the histogram in polar coordinates. This makes it easier to filter out the unwanted points according to the radius from the center.

import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
import numpy as np; np.random.seed(1)

r = np.ones(100)*0.9
phi = np.random.rand(100)*2.*np.pi

hist, xedges, yedges = np.histogram2d(r, phi, bins=25, range=[[0, 1.2], [0,2*np.pi*26./25]])
R,Phi = np.meshgrid(xedges[:-1], yedges[:-1])
X = R*np.cos(Phi)
Y = -R*np.sin(Phi) 

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
X[(R < 0.75) | (R > 1)] = np.nan
ax.plot_surface(X,Y, hist.T, alpha=0.2)
ax.plot_wireframe(X,Y, hist.T)
plt.show()