CODEWITHSUNDEEP
pythonpandasdataframedatetime
Tim Williams
Tim Williams

Reputation: 35

Counting the number of rows by year with a DateTime Index

I have a DataFrame which has a DateTime index as such

enter image description here

What I would like to do would be to find how many rows/instances occur by year. E.g. how many instances occur in the year 2013, 2014 ... 2020.

I would like to return this as a series or dataframe which I can then use to plot to show how many instances there were per year e.g.

2013 20
2014 14
.
.
.
2020 25

Is there a way to use the groupby or another function on the datetime index to return the counts of how many rows there are per year?

Upvotes: 0

Views: 1184

Answers (1)

Pablo C
Pablo C

Reputation: 4761

You can use pandas.DataFrame.groupby with a callable:

df.groupby(lambda x: x.year).size()

When you use groupby this way, the callable works directly with the indices.

This is equivalent to:

def func(date):
    return date.year

df.groupby(func).size()

Since you're working with pandas.Timestamp you can easily access to the year attribute.

Upvotes: 1

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