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51 changes: 49 additions & 2 deletions pandas/core/series.py
Original file line number Diff line number Diff line change
Expand Up @@ -1607,16 +1607,63 @@ def cov(self, other, min_periods=None):

def diff(self, periods=1):
"""
1st discrete difference of object
First discrete difference of element.

Calculates the difference of a Series element compared with another
element in the Series (default is element in previous row).

Parameters
----------
periods : int, default 1
Periods to shift for forming difference
Periods to shift for calculating difference, accepts negative
values.

Returns
-------
diffed : Series

See Also
--------
Series.pct_change: Percent change over given number of periods.
Series.shift: Shift index by desired number of periods with an
optional time freq.
DataFrame.diff: First discrete difference of object

Examples
--------
Difference with previous row

>>> s = pd.Series([1, 1, 2, 3, 5, 8])
>>> s.diff()
0 NaN
1 0.0
2 1.0
3 1.0
4 2.0
5 3.0
dtype: float64

Difference with 3rd previous row

>>> s.diff(periods=3)
0 NaN
1 NaN
2 NaN
3 2.0
4 4.0
5 6.0
dtype: float64

Difference with following row

>>> s.diff(periods=-1)
0 0.0
1 -1.0
2 -1.0
3 -2.0
4 -3.0
5 NaN
dtype: float64
"""
result = algorithms.diff(com._values_from_object(self), periods)
return self._constructor(result, index=self.index).__finalize__(self)
Expand Down