bar plot in 3d following a given line-CodePudding

I want to draw a bar plot in 3d. I know how to do that using the following code:

from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as plt
import numpy as np
fig = plt.figure(figsize=(10,10))
ax = fig.add_subplot(111, projection='3d')
nbins = 50
# for c, z in zip(['r', 'g', 'b', 'y'], [30, 20, 10, 0]):
ys = np.random.normal(loc=10, scale=10, size=2000)

hist, bins = np.histogram(ys, bins=nbins)
xs = (bins[:-1]   bins[1:])/2

ax.bar(xs, hist, zs=30, zdir='y', color='r', ec='r', alpha=0.8)

ax.set_xlabel('X')
ax.set_ylabel('Y')
ax.set_zlabel('Z')

plt.show()

This will render something like this:

EDIT to explain what is going on:

Consider a generic rectangle with 4 vertices: bottom left, bottom right, top right, top left. For simplicity, let's fix width=height=1. Then we consider a reference system x,y,z and we draw this rectangle. The coordinates of vertices are: bottom left (-0.5, 0, 0), bottom right (0.5, 0, 0), top right (0.5, 0, 1) and top left (-0.5, 0, 1). Note that this rectangle is centered around the zero in the x direction. If we move it to x=2, then it will be centered at that location. You can see the above coordinates in rect: why does this variable has a fourth column filled with ones? That's a mathematical trick to be able to apply a translation matrix to the vertices.

Let's talk about transformation matrices (wikipedia has a nice page about it). Consider again our generic rectangle: we can scale it, rotate it and translate it to get a new rectangle in the position and orientation we want.

So, the code above defines a function for each transformation, translate, scale, rotate. Turns out that we can multiply together multiple transformation matrices to get an overall transformation: that's what transformation_matrix does, it combines the aforementioned transformations into a single matrix.

Finally, I used apply_transform to apply the transformation matrix to the generic rectangle: this will compute the coordinates of the vertices of the new rectangle, in the specified position/orientation with the specified size (width, height).