Plotting histograms against classes in pandas / matplotlib

Question

Is there a idiomatic way to plot the histogram of a feature for two classes? In pandas, I basically want

df.feature[df.class == 0].hist() df.feature[df.class == 1].hist() 

To be in the same plot. I could do

df.feature.hist(by=df.class) 

but that gives me two separate plots.

This seems to be a common task so I would imagine there to be an idiomatic way to do this. Of course I could manipulate the histograms manually to fit next to each other but usually pandas does that quite nicely.

Basically I want this matplotlib example in one line of pandas: http://matplotlib.org/examples/pylab_examples/barchart_demo.html

I thought I was missing something, but maybe it is not possible (yet).

Answer 1

How about df.groupby("class").feature.hist()? To see overlapping distributions you'll probably need to pass alpha=0.4 to hist(). Alternatively, I'd be tempted to use a kernel density estimate instead of a histogram with df.groupby("class").feature.plot(kind='kde').

As an example, I plotted the iris dataset's classes using:

iris.groupby("Name").PetalWidth.plot(kind='kde', ax=axs[1]) iris.groupby("Name").PetalWidth.hist(alpha=0.4, ax=axs[0])