Question

我有一个数据框，需要从基线开始进行燃尽并减去所有值，本质上我正在寻找 DataFrame（）。cumsum（0）的对面：

               In Use
Baseline       3705.0
February 2018     0.0
March 2018        2.0
April 2018       15.0
May 2018         30.0
June 2018        14.0
July 2018       797.0
August 2018    1393.0
September 2018   86.0
October 2018    374.0
November 2018    21.0
December 2018     0.0
January 2019      0.0
February 2019     0.0
March 2019        0.0
April 2019        2.0
unknown         971.0

我找不到要执行的功能，或者找不到正确的标签/名称。

如何实现？

Answer 1

按DataFrameGroupBy.diff创建的组使用diff，按lt <进行共同映射并累积总和：

g = df['Use'].diff().lt(0).cumsum()
df['new'] = df['Use'].groupby(g).diff().fillna(df['Use'])
print (df)
                In     Use     new
0         Baseline  3705.0  3705.0
1    February 2018     0.0     0.0
2       March 2018     2.0     2.0
3       April 2018    15.0    13.0
4         May 2018    30.0    15.0
5        June 2018    14.0    14.0
6        July 2018   797.0   783.0
7      August 2018  1393.0   596.0
8   September 2018    86.0    86.0
9     October 2018   374.0   288.0
10   November 2018    21.0    21.0
11   December 2018     0.0     0.0
12    January 2019     0.0     0.0
13   February 2019     0.0     0.0
14      March 2019     0.0     0.0
15      April 2019     2.0     2.0
16         unknown   971.0   969.0

Answer 2

您可以将pd.Series.diff与fillna一起使用。这是一个演示：

df = pd.DataFrame({'A': np.random.randint(0, 10, 5)})

df['B'] = df['A'].cumsum()
df['C'] = df['B'].diff().fillna(df['B']).astype(int)

print(df)

   A   B  C
0  1   1  1
1  4   5  4
2  4   9  4
3  2  11  2
4  1  12  1

列中的熊猫累积减法

2 个答案: