Matplotlib bar3d variable alpha

问题:

I'm using matplotlib bar3d with RdBu colormap and wanted to have variable transparency between bars (so smaller bars can be more transparent than taller bars).

Here is the code for making the 3d bar plot. The data is stored in a 4x4 matrix 'rho'. At the moment alpha is kept at 0.95, but it would be excellent to be able to control the value of alpha for each bar.

Cheers

xpos = np.arange(0,4,1)
ypos = np.arange(0,4,1)
xpos, ypos = np.meshgrid(xpos, ypos)
xpos = xpos.flatten()
ypos = ypos.flatten()
zpos = np.zeros(4*4)
dx = 0.5 * np.ones_like(zpos)
dy = dx.copy()
dz = rho.flatten()
nrm=mpl.colors.Normalize(-1,1)
colors=cm.RdBu(nrm(-dz))
alpha = 0.95
ax.bar3d(xpos,ypos,zpos, dx, dy, dz, alpha=alpha, color=colors, linewidth=0)

回答1:

xpos = np.arange(0,4,1)
ypos = np.arange(0,4,1)
xpos, ypos = np.meshgrid(xpos, ypos)
xpos = xpos.flatten()
ypos = ypos.flatten()
zpos = np.zeros(4*4)
rho = np.random.random((4,4))
dx = 0.5 * np.ones_like(zpos)
dy = dx.copy()
dz = rho.flatten()
nrm=mpl.colors.Normalize(-1,1)
colors=cm.RdBu(nrm(-dz))
alpha = np.linspace(0.2, 0.95, len(xpos), endpoint=True)
fig = plt.figure()
ax = fig.gca(projection='3d')
for i in range(len(xpos)):
    ax.bar3d(xpos[i],ypos[i],zpos[i], dx[i], dy[i], dz[i], alpha=alpha[i], color=colors[i], linewidth=0)
plt.show()