Calculating returns from a dataframe with financial data

Question

I have a dataframe with monthly financial data:

In [89]: vfiax_monthly.head()
Out[89]: 
            year  month  day       d   open  close   high    low  volume          


        

Answer 1

Could also use a mix of diff and shift methods of pandas series:

retrun = vfiax_monthly.open.diff()/vfiax_monthly.open.shift(1)