CODEWITHSUNDEEP
pythonpandas
Shan
Shan

Reputation: 55

Cumulative sum starting from the right

I've got a dataframe which in general form looks like this.

   A  B  C
0  1  2  3
1  2  4  6
2  3  5  7

I'd like to create another dataframe where in each value is the cumulative sum along the row of values in the original dataframe, starting from the right, rather than the left - i.e. the output should look like this: 

   A  B  C
0  6  5  3
1  12 10 6
2  ...

Can anyone suggest a bit of code to do this?

Upvotes: 2

Views: 803

Answers (1)

jezrael
jezrael

Reputation: 863741

Use iloc for reversing values twice:

df = df.iloc[:, ::-1].cumsum(axis=1).iloc[:, ::-1]
print (df)
    A   B  C
0   6   5  3
1  12  10  6
2  15  12  7

#first reverse values
print (df.iloc[:, ::-1])
   C  B  A
0  3  2  1
1  6  4  2
2  7  5  3

#then use function cumsum
print (df.iloc[:, ::-1].cumsum(axis=1))
   C   B   A
0  3   5   6
1  6  10  12
2  7  12  15

#last reverse back 
print (df.iloc[:, ::-1].cumsum(axis=1).iloc[:, ::-1])

    A   B  C
0   6   5  3
1  12  10  6
2  15  12  7

Upvotes: 4

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