How to compute cumulative sum of previous N rows in pandas?

Question

I am working with pandas, but I don\'t have so much experience. I have the following DataFrame:

          A
0       NaN
1      0.00
2      0.00
3      3.33
4         


        

Answer 1

Check the pandas.Series.expanding. The series.expanding(min_periods=2).sum()

will do the job for you. And don't forget to set 0-th element, since it is NaN. I mean,

accumulation = series.expanding(min_periods=2).sum()
accumulation[0] = series[0] # or as you like