Remove by column in pandas.DataFrame.hist

After specifying grouping by column a and restricting to column f and g for histogram, I still have column a showing up in green. Is there a way to remove it without going into matplotlib or for loop?

axes = dfs.hist(column=['f', 'g'], by='a', layout=(1, 3), legend=True, bins=np.linspace(0, 8, 10),
            sharex=True, sharey=True)

Answer

This is clearly a bug with the pandas library. The problem seems to arise when by is a numeric dtype column — it probably subsets the DataFrame to the labels in column and by and then plots that, which is problematic when by is numeric.

You can either create non-numeric labels for the column that defines your 'by', or if you don’t want to change your data, it suffices to re-assign the type to object just before the plot.

Sample Data

import pandas as pd
import numpy as np

df = pd.DataFrame({'length': np.random.normal(0, 1, 1000),
                   'width': np.random.normal(0, 1, 1000),
                   'a': np.random.randint(0, 2, 1000)})

---

# Problem with a numeric dtype for `by` column
df.hist(column=['length', 'width'], by='a', figsize=(4, 2))

# Works fine when column type is object
(df.assign(a=df['a'].astype('object'))
   .hist(column=['length', 'width'], by='a' , figsize=(4, 2)))