how to get different line colors depending on one variable for different plots in one single figure in python?

Question

Let's say I have one figure with a certain number of plots, which resembles like this one:

where the colors of the single plots are decided automatically by matplotlib. The code to obtain this is very simple:

for i in range(len(some_list)):
    x, y = some_function(dataset, some_list[i])
    plt.plot(x, y) 

Now suppose that all these lines depend on a third variable z. I would like to include this information plotting the given lines with a color that gives information about the magnitude of z, possibly using a colormap and a colorbar on the right side of the figure. What would you suggest me to do? I exclude to use a legend since in my figures I have many more lines that the ones I am showing. All information I can find is about how to draw one single line with different colors, but this is not what I am looking for. I thank you in advance!

Answer 1

Here it is some code that, in my opinion, you can easily adapt to your problem

import numpy as np
import matplotlib.pyplot as plt
from random import randint

# generate some data
N, vmin, vmax = 12, 0, 20
rd = lambda: randint(vmin, vmax)
segments_z = [((rd(),rd()),(rd(),rd()),rd()) for _ in range(N)]

# prepare for the colorization of the lines,
# first the normalization function and the colomap we want to use
norm = plt.Normalize(vmin, vmax)
cm = plt.cm.rainbow
# most important, plt.plot doesn't prepare the ScalarMappable
# that's required to draw the colorbar, so we'll do it instead
sm = plt.cm.ScalarMappable(cmap=cm, norm=norm)

# plot the segments, the segment color depends on z
for p1, p2, z in segments_z:
    x, y = zip(p1,p2)
    plt.plot(x, y, color=cm(norm(z)))

# draw the colorbar, note that we pass explicitly the ScalarMappable
plt.colorbar(sm)

# I'm done, I'll show the results,
# you probably want to add labels to the axes and the colorbar.
plt.show()