plot arrays by row with matplotlib

Question

I have two numpy arrays (a and b) with shape (16, 850) each. I'm displaying them row by row, e.g.

plt.figure()
plt.plot(a[0], b[0])
plt.plot(a[1], b[1]) 
plt.plot(a[2], b[2])
...
plt.show()

Should I have to use a for loop to do it in a more pythonic way?

Suever · Accepted Answer · 2016-08-14T16:04:44.360

14

You can pass a multi-dimensional array to plot and each column will be created as a separate plot object. We transpose both inputs so that it will plot each row separately.

a = np.random.rand(16, 850)
b = np.random.rand(16, 850)

plt.plot(a.T, b.T)
plt.show()

edited Aug 14 '16 at 16:04

answered Aug 14 '16 at 15:59

Suever

64,497
14
82
101

Thanks @Suever. That worked because I needed to display 16 plots. That's why I said "row by row" :) – Maxwell's Daemon Aug 14 '16 at 16:04

score 0 · Answer 2 · answered Aug 14 '16 at 15:59

0

This will work:

plt.figure()
for i in range(len(a)):
    plt.plot(a[i], b[i])
plt.show()

But the way that Suever shows is much Pythonic. However, not every function has something like that built-in.

answered Aug 14 '16 at 15:59

Mathias711

6,568
4
41
58

score 0 · Answer 3 · answered Feb 06 '19 at 00:16

The most efficient way to draw many lines is the use of a LineCollection. This might look like

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.collections import LineCollection

x = np.random.rand(N,3)
y = np.random.rand(N,3)

data = np.stack((x,y), axis=2)
fig, ax = plt.subplots()

ax.add_collection(LineCollection(data))

for a bunch of lines consisting of 3 points each.

Find a comparisson for different methods and their efficiency in the answer to Many plots in less time - python.

plot arrays by row with matplotlib

3 Answers3