在pandas数据框中创建一列，该列计算两行之间的差异

Question

I want to create a new column called df[column_name] , where the result is the difference between the current row and the row above it.

In the case of the first row there is nothing above it so change is 0. for the second row change is 2 (26-24) and so on.

dates | data | result
24-09    24      0
25-09    26      2
26-09    27      1
27-09    28      1
28-09    26     -2

Answer 1

You can use the diff method for this, together with fillna to fill the first NaN with a 0:

df['data'].diff().fillna(0)

Example:

In [6]: df = pd.DataFrame({'data':[24,26,27,28,26]})

In [7]: df['result'] = df['data'].diff().fillna(0)

In [8]: df
Out[8]: 
   data  result
0    24       0
1    26       2
2    27       1
3    28       1
4    26      -2