CODEWITHSUNDEEP
pythonpandasapply
andream
andream

Reputation: 43

Cumulative custom function

I am trying to add a column to a pandas dataframe 

import pandas as pd
df = pd.DataFrame([['a',1],['b',0],['c',1],['d',1],['e',0],['f',1]])

such that it contains the result of a cumulative custom function

a --> (total + a) * a

that is, it takes the value a, sums it up with the total and multiplies the result. In my example I would like to have as output:

pd.DataFrame([['a',1,1],['b',0,0],['c',1,1],['d',1,2],['e',0,0],['f',1,1]])

I understand that this could be done using 

df.expanding.apply(some_lambda_function)

but I have some difficult in understanding how to code it.

Do you have any idea?

many thanks.

Upvotes: 2

Views: 166

Answers (1)

BENY
BENY

Reputation: 323306

I will recommend for loop ..

start=0
total=[]
for x ,y in df.iterrows():
    start=(y[1]+start)*y[1]
    total.append(start)
total
Out[201]: [1, 0, 1, 2, 0, 1]

Upvotes: 1

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