Updating a matplotlib bar graph?

Question

I have a bar graph which retrieves its y values from a dict. Instead of showing several graphs with all the different values and me having to close every single one, I need it to update values on the same graph. Is there a solution for this?

Answer 1

Here is an example of how you can animate a bar plot. You call plt.bar only once, save the return value rects, and then call rect.set_height to modify the bar plot. Calling fig.canvas.draw() updates the figure.

import matplotlib
matplotlib.use('TKAgg')
import matplotlib.pyplot as plt
import numpy as np

def animated_barplot():
    # http://www.scipy.org/Cookbook/Matplotlib/Animations
    mu, sigma = 100, 15
    N = 4
    x = mu + sigma*np.random.randn(N)
    rects = plt.bar(range(N), x,  align = 'center')
    for i in range(50):
        x = mu + sigma*np.random.randn(N)
        for rect, h in zip(rects, x):
            rect.set_height(h)
        fig.canvas.draw()

fig = plt.figure()
win = fig.canvas.manager.window
win.after(100, animated_barplot)
plt.show()

Answer 2

I've simplified the above excellent solution to its essentials, with more details at my blogpost:

import numpy as np
import matplotlib.pyplot as plt

numBins = 100
numEvents = 100000

file = 'datafile_100bins_100000events.histogram'
histogramSeries = np.loadtext(file)

fig, ax = plt.subplots()
rects = ax.bar(range(numBins), np.ones(numBins)*40)  # 40 is upper bound of y-axis 

for i in range(numEvents):
    for rect,h in zip(rects,histogramSeries[i,:]):
        rect.set_height(h)
    fig.canvas.draw()
    plt.pause(0.001)