Pyplot: vertical gradient fill under curve?

Question

I'm wondering if there's a way to fill under a pyplot curve with a vertical gradient, like in this quick mockup:

I found this hack on StackOverflow, and I don't mind the polygons if I could figure out how to make the color map vertical: How to fill rainbow color under a curve in Python matplotlib

score 13 · Answer 1 · answered Feb 27 '14 at 22:13

13

There may be a better way, but here goes:

from matplotlib import pyplot as plt

x = range(10)
y = range(10)
z = [[z] * 10 for z in range(10)]
num_bars = 100  # more bars = smoother gradient

plt.contourf(x, y, z, num_bars)

background_color = 'w'
plt.fill_between(x, y, y2=max(y), color=background_color)

plt.show()

Shows:

enter image description here

answered Feb 27 '14 at 22:13

mdscruggs

1,182
7
15

1

That's pretty good thinking outside the box, having a gradient background and a white fill over it. It would not have occurred to me any time soon. – prooffreader Feb 27 '14 at 23:32
instead of `plt.contourf` I would use `plt.imshow` for the gradient fill. See [my answer to this other question](http://stackoverflow.com/a/42971319/4375377). – Mr Tsjolder from codidact Mar 23 '17 at 09:05

score 7 · Answer 2 · edited Nov 07 '19 at 22:19

There is an alternative solution closer to the sketch in the question. It's given on Henry Barthes' blog http://pradhanphy.blogspot.com/2014/06/filling-between-curves-with-color.html. This applies an imshow to each of the patches, I've copied the code in case the link changes,

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.path import Path
from matplotlib.patches import PathPatch

xx=np.arange(0,10,0.01)
yy=xx*np.exp(-xx)

path = Path(np.array([xx,yy]).transpose())
patch = PathPatch(path, facecolor='none')
plt.gca().add_patch(patch)

im = plt.imshow(xx.reshape(yy.size,1),   
                cmap=plt.cm.Reds,
                interpolation="bicubic",
                origin='lower',
                extent=[0,10,-0.0,0.40],
                aspect="auto",
                clip_path=patch, 
                clip_on=True)
plt.show()

Pyplot: vertical gradient fill under curve?

2 Answers2

Linked

Related