CODEWITHSUNDEEP
pythonmatplotlib
Tensza
Tensza

Reputation: 213

Matplotlib animated histogram colormap/gradient

I am trying to animate a histogram using matplotlib and I want to show the different bars using a colormap, e.g:

current animated histograms

I have this working when I clear the complete figure every frame and then redraw everything. But this is very slow, so I am trying out the example by matplotlib itself.

This works and is very fast, but unfortunately I have no idea on how to specify a colormap because it is using the patches.PathPatch object to draw the histogram now. I can only get it to work with the same single color for every individual bar.

How can I specify a gradient or colormap to achieve the desired result shown above?

Here is an example of a working animation with a single color which I am currently using.

import numpy as np

import matplotlib.pyplot as plt
import matplotlib.patches as patches
import matplotlib.path as path
import matplotlib.animation as animation

# Fixing random state for reproducibility
np.random.seed(19680801)

# histogram our data with numpy
data = np.random.randn(1000)
n, bins = np.histogram(data, 100)

# get the corners of the rectangles for the histogram
left = np.array(bins[:-1])
right = np.array(bins[1:])
bottom = np.zeros(len(left))
top = bottom + n
nrects = len(left)

nverts = nrects * (1 + 3 + 1)
verts = np.zeros((nverts, 2))
codes = np.ones(nverts, int) * path.Path.LINETO
codes[0::5] = path.Path.MOVETO
codes[4::5] = path.Path.CLOSEPOLY
verts[0::5, 0] = left
verts[0::5, 1] = bottom
verts[1::5, 0] = left
verts[1::5, 1] = top
verts[2::5, 0] = right
verts[2::5, 1] = top
verts[3::5, 0] = right
verts[3::5, 1] = bottom

patch = None


def animate(i):
    # simulate new data coming in
    data = np.random.randn(1000)
    n, bins = np.histogram(data, 100)
    top = bottom + n
    verts[1::5, 1] = top
    verts[2::5, 1] = top
    return [patch, ]

fig, ax = plt.subplots()
barpath = path.Path(verts, codes)
patch = patches.PathPatch(
    barpath, facecolor='green', edgecolor='yellow', alpha=0.5)
ax.add_patch(patch)

ax.set_xlim(left[0], right[-1])
ax.set_ylim(bottom.min(), top.max())

ani = animation.FuncAnimation(fig, animate, 100, repeat=False, blit=True)
plt.show()

Upvotes: 2

Views: 446

Answers (1)

Jiadong
Jiadong

Reputation: 2072

I recommend u using BarContainer, you can change bar color individually. In your example, the path is single object, matplotlib seems not to support gradient color for a single patch (not sure though).

import numpy as np
import matplotlib.pyplot as plt
# Fixing random state for reproducibility
np.random.seed(19680801)

# histogram our data with numpy
data = np.random.randn(1000)
colors = plt.cm.coolwarm(np.linspace(0, 1, 100))

    
def animate(i):
    data = np.random.randn(1000)
    bc = ax.hist(data, 100)[2]
    for i, e in enumerate(bc):
        e.set_color(colors[i])
    return bc

fig, ax = plt.subplots(1, 1, figsize=(7.2, 7.2))

ani = animation.FuncAnimation(fig, animate, 100, repeat=False, blit=True)

Upvotes: 1

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