Visualization of 3D vector using matplotlib

Question

I am trying to visualize two 3D column vectors using matplotlib. Here are the vector

v1 = (0, 2 , 1)
v2 = (2, 2, 0)

The visualization for the above vectors that I got from the book.

[Source: Introduction to Linear Algebra, Fifth Edition (2016), by Gilbert Strang ]

I am trying to to visualize the same. Here is code and the plot.


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

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

soa = np.array([[0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0],
                [0, 0, 0, 0, 0, 0], [0, 0, 4, 0.5, 0.7, 0]])

X, Y, Z, U, V, W = zip(*soa)
ax.quiver(X, Y, Z, U, V, W)
ax.set_xlim([-1, 5])
ax.set_ylim([-1, 5])
ax.set_zlim([-1, 8])
plt.show()

View:

I am not sure about the view. is it correct? Need help if I am wrong here.

Zephyr · Accepted Answer · 2021-09-08 10:44:36Z

1

With the line:

soa = np.array([[0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0],
                [0, 0, 0, 0, 0, 0], [0, 0, 4, 0.5, 0.7, 0]])

you are defining 4 3D vectors, 3 of which have 0 length, the last one starts from (0, 0, 4) and has components (0.5, 0.7, 0). So the code is compliant with the image you reported.
If you want to plot the vectors v1 and v2, both starting from origin, you should use:

soa = np.array([[0, 0, 0, 0, 2, 1], [0, 0, 0, 2, 2, 0]])

Complete Code

import numpy as np
import matplotlib.pyplot as plt


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

soa = np.array([[0, 0, 0, 0, 2, 1], [0, 0, 0, 2, 2, 0]])

X, Y, Z, U, V, W = zip(*soa)
ax.quiver(X, Y, Z, U, V, W)
ax.set_xlim([-1, 5])
ax.set_ylim([-1, 5])
ax.set_zlim([-1, 8])
ax.set_xlabel('x')
ax.set_ylabel('y')
ax.set_zlabel('z')

plt.show()

answered Sep 8, 2021 at 10:44

Zephyr

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3 Comments

Arijit Panda Over a year ago

Thanks. By mistake I copied different code. But Now I know the answer.

Arijit Panda Over a year ago

do you have any idea to set this view (without rotating by hand manually) by code only ?

Zephyr Over a year ago

Try to take a look to this answer

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