python - How to plot 2d math vectors with matplotlib?

Question

How can we plot 2D math vectors with matplotlib? Does anyone have an example or suggestion about that?

I have a couple of vectors stored as 2D numpy arrays, and I would like to plot them as directed edges.

The vectors to be plotted are constructed as below:

import numpy as np
# a list contains 3 vectors;
# each list is constructed as the tail and the head of the vector
a = np.array([[0, 0, 3, 2], [0, 0, 1, 1], [0, 0, 9, 9]]) 

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Edit:

I just added the plot of the final answer of tcaswell for anyone interested in the output and want to plot 2d vectors with matplotlib:

Answer 1

The suggestion in the comments by halex is correct, you want to use quiver (doc), but you need to tweak the properties a bit.

import numpy as np
import matplotlib.pyplot as plt

soa = np.array([[0, 0, 3, 2], [0, 0, 1, 1], [0, 0, 9, 9]])
X, Y, U, V = zip(*soa)
plt.figure()
ax = plt.gca()
ax.quiver(X, Y, U, V, angles='xy', scale_units='xy', scale=1)
ax.set_xlim([-1, 10])
ax.set_ylim([-1, 10])
plt.draw()
plt.show()