DOC: update the pandas.DataFrame.diff docstring (pandas-dev#20227)

* DOC: update the pandas.DataFrame.diff  docstring

* DOC: update the pandas.DataFrame.diff docstring

* DOC: update the pandas.DataFrame.diff docstring

* DOC: update the pandas.DataFrame.diff docstring

* DOC: update the pandas.DataFrame.diff docstring

* DOC: update the pandas.DataFrame.diff  docstring

* DOC: update the pandas.DataFrame.diff  docstring

* DOC: update the pandas.DataFrame.diff  docstring

* DOC: update the pandas.DataFrame.diff docstring

* Cleanup

Author: adatasetaday

Diff for: pandas/core/frame.py

@@ -4770,20 +4770,90 @@ def melt(self, id_vars=None, value_vars=None, var_name=None,
 
     def diff(self, periods=1, axis=0):
         """
-        1st discrete difference of object
+        First discrete difference of element.
+
+        Calculates the difference of a DataFrame element compared with another
+        element in the DataFrame (default is the element in the same column
+        of the previous row).
 
         Parameters
         ----------
         periods : int, default 1
-            Periods to shift for forming difference
+            Periods to shift for calculating difference, accepts negative
+            values.
         axis : {0 or 'index', 1 or 'columns'}, default 0
             Take difference over rows (0) or columns (1).
 
-            .. versionadded:: 0.16.1
+            .. versionadded:: 0.16.1.
 
         Returns
         -------
         diffed : DataFrame
+
+        See Also
+        --------
+        Series.diff: First discrete difference for a Series.
+        DataFrame.pct_change: Percent change over given number of periods.
+        DataFrame.shift: Shift index by desired number of periods with an
+            optional time freq.
+
+        Examples
+        --------
+        Difference with previous row
+
+        >>> df = pd.DataFrame({'a': [1, 2, 3, 4, 5, 6],
+        ...                    'b': [1, 1, 2, 3, 5, 8],
+        ...                    'c': [1, 4, 9, 16, 25, 36]})
+        >>> df
+           a  b   c
+        0  1  1   1
+        1  2  1   4
+        2  3  2   9
+        3  4  3  16
+        4  5  5  25
+        5  6  8  36
+
+        >>> df.diff()
+             a    b     c
+        0  NaN  NaN   NaN
+        1  1.0  0.0   3.0
+        2  1.0  1.0   5.0
+        3  1.0  1.0   7.0
+        4  1.0  2.0   9.0
+        5  1.0  3.0  11.0
+
+        Difference with previous column
+
+        >>> df.diff(axis=1)
+            a    b     c
+        0 NaN  0.0   0.0
+        1 NaN -1.0   3.0
+        2 NaN -1.0   7.0
+        3 NaN -1.0  13.0
+        4 NaN  0.0  20.0
+        5 NaN  2.0  28.0
+
+        Difference with 3rd previous row
+
+        >>> df.diff(periods=3)
+             a    b     c
+        0  NaN  NaN   NaN
+        1  NaN  NaN   NaN
+        2  NaN  NaN   NaN
+        3  3.0  2.0  15.0
+        4  3.0  4.0  21.0
+        5  3.0  6.0  27.0
+
+        Difference with following row
+
+        >>> df.diff(periods=-1)
+             a    b     c
+        0 -1.0  0.0  -3.0
+        1 -1.0 -1.0  -5.0
+        2 -1.0 -1.0  -7.0
+        3 -1.0 -2.0  -9.0
+        4 -1.0 -3.0 -11.0
+        5  NaN  NaN   NaN
         """
         bm_axis = self._get_block_manager_axis(axis)
         new_data = self._data.diff(n=periods, axis=bm_axis)