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DOC: Add recipe for shifting groups of values based on the index #6917

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Apr 21, 2014
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DOC: Add recipe for shifting groups of values based on the index #6917

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13 changes: 13 additions & 0 deletions doc/source/cookbook.rst
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Expand Up @@ -191,6 +191,19 @@ The :ref:`grouping <groupby>` docs.
`Create a value counts column and reassign back to the DataFrame
<http://stackoverflow.com/questions/17709270/i-want-to-create-a-column-of-value-counts-in-my-pandas-dataframe>`__

`Shift groups of the values in a column based on the index
<http://stackoverflow.com/q/23198053/190597>`__

.. ipython:: python

df = pd.DataFrame(
{u'line_race': [10L, 10L, 8L, 10L, 10L, 8L],
u'beyer': [99L, 102L, 103L, 103L, 88L, 100L]},
index=[u'Last Gunfighter', u'Last Gunfighter', u'Last Gunfighter',
u'Paynter', u'Paynter', u'Paynter']); df

df['beyer_shifted'] = df.groupby(level=0)['beyer'].apply(lambda grp: grp.shift(1))
df

Expanding Data
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