Time-series boxplot in pandas

Question

How can I create a boxplot for a pandas time-series where I have a box for each day?

Sample dataset of hourly data where one box should consist of 24 values:

import pandas as pd
n = 480
ts = pd.Series(randn(n),
               index=pd.date_range(start="2014-02-01",
                                   periods=n,
                                   freq="H"))
ts.plot()

I am aware that I could make an extra column for the day, but I would like to have proper x-axis labeling and x-limit functionality (like in ts.plot()), so being able to work with the datetime index would be great.

There is a similar question for R/ggplot2 here, if it helps to clarify what I want.

Answer 1

I have a solution that may be helpful-- It only uses native pandas and allows for hierarchical date-time grouping (i.e spanning years). The key is that if you pass a function to groupby(), it will be called on each element of the dataframe's index. If your index is a DatetimeIndex (or similar), you can access all of the dt's convenience functions for resampling!

Try this:

n = 480
ts = pd.DataFrame(np.random.randn(n), index=pd.date_range(start="2014-02-01", periods=n, freq="H"))
ts.groupby(lambda x: x.strftime("%Y-%m-%d")).boxplot(subplots=False, figsize=(12,9), rot=90)