python - Is there a parameter in matplotlib/pandas to have the Y axis of a histogram as percentage?

Question

I would like to compare two histograms by having the Y axis show the percentage of each column from the overall dataset size instead of an absolute value. Is that possible? I am using Pandas and matplotlib. Thanks

Answer 1

The density=True (normed=True for matplotlib < 2.2.0) returns a histogram for which np.sum(pdf * np.diff(bins)) equals 1. If you want the sum of the histogram to be 1 you can use Numpy's histogram() and normalize the results yourself.

x = np.random.randn(30)

fig, ax = plt.subplots(1,2, figsize=(10,4))

ax[0].hist(x, density=True, color='grey')

hist, bins = np.histogram(x)
ax[1].bar(bins[:-1], hist.astype(np.float32) / hist.sum(), width=(bins[1]-bins[0]), color='grey')

ax[0].set_title('normed=True')
ax[1].set_title('hist = hist / hist.sum()')

Btw: Strange plotting glitch at the first bin of the left plot.