pandas 数据帧 - 运行总和与重置 [英] Pandas dataframe - running sum with reset
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问题描述
我想计算给定列中的运行总和(当然不使用循环)。请注意,我有另一列指定何时将运行总和重置为该行中存在的值。通过以下示例解释最好:
I want to calculate the running sum in a given column(without using loops, of course). The caveat is that I have this other column that specifies when to reset the running sum to the value present in that row. Best explained by the following example:
reset val desired_col
0 0 1 1
1 0 5 6
2 0 4 10
3 1 2 2
4 1 -1 -1
5 0 6 5
6 0 4 9
7 1 2 2
desired_col
是我想要的值
推荐答案
你可以使用2次 cumsum()
/ p>
You can use 2 times cumsum()
:
# reset val desired_col
#0 0 1 1
#1 0 5 6
#2 0 4 10
#3 1 2 2
#4 1 -1 -1
#5 0 6 5
#6 0 4 9
#7 1 2 2
df['cumsum'] = df['reset'].cumsum()
#cumulative sums of groups to column des
df['des']= df.groupby(['cumsum'])['val'].cumsum()
print df
# reset val desired_col cumsum des
#0 0 1 1 0 1
#1 0 5 6 0 6
#2 0 4 10 0 10
#3 1 2 2 1 2
#4 1 -1 -1 2 -1
#5 0 6 5 2 5
#6 0 4 9 2 9
#7 1 2 2 3 2
#remove columns desired_col and cumsum
df = df.drop(['desired_col', 'cumsum'], axis=1)
print df
# reset val des
#0 0 1 1
#1 0 5 6
#2 0 4 10
#3 1 2 2
#4 1 -1 -1
#5 0 6 5
#6 0 4 9
#7 1 2 2
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