python - Matplotlib Plot Lines with Colors Through Colormap

Question

I am plotting multiple lines on a single plot and I want them to run through the spectrum of a colormap, not just the same 6 or 7 colors. The code is akin to this:

for i in range(20):
     for k in range(100):
          y[k] = i*x[i]
     plt.plot(x,y)
plt.show()

Both with colormap "jet" and another that I imported from seaborn, I get the same 7 colors repeated in the same order. I would like to be able to plot up to ~60 different lines, all with different colors.

Answer 1

The Matplotlib colormaps accept an argument (0..1, scalar or array) which you use to get colors from a colormap. For example:

col = plt.cm.jet([0.25,0.75])    

Gives you an array with (two) RGBA colors:

array([[ 0. , 0.50392157, 1. , 1. ], [ 1. , 0.58169935, 0. , 1. ]])

You can use that to create N different colors:

import numpy as np
import matplotlib.pylab as pl

x = np.linspace(0, 2*np.pi, 64)
y = np.cos(x) 

pl.figure()
pl.plot(x,y)

n = 20
colors = pl.cm.jet(np.linspace(0,1,n))

for i in range(n):
    pl.plot(x, i*y, color=colors[i])