multicolor line on matplotlib

Question

Is it possible to have something similar to edgecolor and facecolor for plt.plot()? I need to plot a curve with a different colored boundary around it for e.g. a segment of the line would look like ||| with the outer lines in a different color and the inner line in a different color. Can this be done using a single plot command rather than plotting three plots?

No it can't. A line is a line, which has no edge. You may define a polygon instead. Or you may draw 3 parallel lines.Depending on the use case this can range from just repeating the call to `plot` 3 times to something like shown in [this answer](https://stackoverflow.com/a/42190453/4124317). — ImportanceOfBeingErnest, Jan 16 '18 at 15:44
@ImportanceOfBeingErnest a line _can_ have an edge if you define its `path_effects` using a `Stroke`. — tmdavison, Jan 16 '18 at 15:54

score 2 · Accepted Answer · answered Jan 16 '18 at 15:48

You can do this using the matplotlib.patheffects module. You can set the path_effect of a line by using the path_effects kwarg.

Specifically in this case, we can use the Stroke class for the outline, and the Normal class for the inner part of the line (this just uses the linewidth and color specified by plt.plot). See the example below.

import matplotlib.pyplot as plt
import matplotlib.patheffects as path_effects
import numpy as np

fig, ax = plt.subplots(1)

ax.plot(np.random.rand(5), linewidth=4, color='r', path_effects=[
    path_effects.Stroke(linewidth=8, foreground='black'),
    path_effects.Normal()
    ])

plt.show()

multicolor line on matplotlib

1 Answers1