DataFrame.diff

函数定义

DataFrame.diff(periods=1, axis=0)

• First discrete difference of element.

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

函数参数

• periods: int, default 1
  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).

• Returns: Dataframe
  First differences of the Series.

例子

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
1 NaN -1   3
2 NaN -1   7
3 NaN -1  13
4 NaN  0  20
5 NaN  2  28

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