Python Pandas - Date Column to Column index

Question

I have a table of data imported from a CSV file into a DataFrame.

The data contains around 10 categorical fields, 1 month column (in date time format) and the rest are data series.

How do I convert the date column into an index across the the column axis?

read_csv does this by itself if you invoke the function with the index_col and parse_dates=True — behzad.nouri
– behzad.nouri, Commented Apr 1, 2013 at 23:16

Andy Hayden · Accepted Answer · 2013-04-01 21:54:37Z

37

You can use set_index:

df.set_index('month')

For example:

In [1]: df = pd.DataFrame([[1, datetime(2011,1,1)], [2, datetime(2011,1,2)]], columns=['a', 'b'])

In [2]: df
Out[2]: 
   a                   b
0  1 2011-01-01 00:00:00
1  2 2011-01-02 00:00:00

In [3]: df.set_index('b')
Out[3]: 
            a
b            
2011-01-01  1
2011-01-02  2

answered Apr 1, 2013 at 21:54

Andy Hayden

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6 Comments

MrHopko Over a year ago

Thanks Andy Can i set the index so that the date is along the other axis? Will this group the values?

Andy Hayden Over a year ago

Could you give an example DataFrame which you have and what you want? I'm not sure how it makes sense to make a date column a column index... It won't group the values, this makes one column the index. :)

MrHopko Over a year ago

I want the data arranged so that each column represents 1 month. Each row in the table represents a different time series. Does that make sense? I would demonstrate with a table but I have no idea how to insert a table on this website.

MrHopko Over a year ago

A related question would be: How do I transfer an item from one index axis to another within a hierarchical index?

Serhii Kushchenko Over a year ago

add inplace=True to set_index, otherwise it does not work as expected

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aysebilgegunduz · Accepted Answer · 2022-07-13 10:52:43Z

7

I had a similar problem and I've just solved by reset_index. But you can use either set_index or reset_index:

df_ind = df.set_index(['A', 'B'])

Or

df.reset_index(level=0, inplace=True)

edited Jul 13, 2022 at 10:52

answered Nov 20, 2014 at 21:14

aysebilgegunduz

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Comments

Shankar ARUL · Accepted Answer · 2015-02-02 16:51:37Z

3

If you don't know the name of the date column ahead of time and need to set the index automatically based on the time series column in the data

df.set_index((df.select_dtypes(include=[np.datetime64]).columns).tolist())

answered Feb 2, 2015 at 16:51

Shankar ARUL

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