matplotlib set_data() 未在下一次绘制时更新 plot()

Question

I have a 2D plot placed on one of the walls of a 3D plot that doesn't seem to reflect any changes from set_data() , I would like to understand what I'm doing wrong here.

Here is a sample code showing the 3D plot with the 2D 'projection' plot in question. The output is shown here:

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

plt.rcParams['legend.fontsize'] = 10

fig = plt.figure()
ax = fig.gca(projection='3d')

# Test data for projection onto xz plane
t = linspace(0,10, num=20)
z = np.sin(t)

# Plot projection
projx, = ax.plot(np.linspace(-1,0, num=len(z)), z, 'r', zdir='y', zs=1)

# Labels and scaling
ax.set_xlabel('M_x')
ax.set_ylabel('M_y')
ax.set_zlabel('M_z')
ax.set_xlim(-1, 1)
ax.set_ylim(-1, 1)
ax.set_zlim(-1, 1)

# Update projection data
projx.set_data([0],[0])

# See if actually updated data
print(projx.get_xdata())

# Draw and display window
plt.draw()
ax.legend()

plt.show()

I imagine that this line:

projx.set_data([0],[0])

would make the projection plot virtually empty. Instead, the sine wave remains.

Furthermore, the printout yields [0] as expected, so the set_data() call was successful, but for some reason the plot doesn't get drawn with the new data.

Shouldn't the set_data() changes be reflected when drawn afterwards?

Answer 1

There is a way to update a Line3D object by directly setting its vertices. Not sure, if this might have any negative side effects, though.

import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.gca(projection='3d')

# Test data for projection onto xz plane
t = np.linspace(0,10, num=20)
z = np.sin(t)

# Plot projections
projx, = ax.plot(np.linspace(-1,0, num=len(z)), z, 'r', zdir='y', zs=1, label="changed")
projy, = ax.plot(np.linspace(-1,0, num=len(z)), z, 'b', zdir='x', zs=-1, label="not changed")

# Labels and scaling
ax.set_xlabel('M_x')
ax.set_ylabel('M_y')
ax.set_zlabel('M_z')
ax.set_xlim(-1, 1)
ax.set_ylim(-1, 1)
ax.set_zlim(-1, 1)

#update vertices of one Line3D object
projx._verts3d = [0, 0.2, 0.7], [1, 1, 1], [0.5, 0.2, 0.7]

ax.legend()
plt.show()

Sample output:

However, since one cannot omit any of the x , y , and z arrays, there is no real advantage over plotting it as a 3D array with one array being a constant.