I have a query regarding Pandas data manipulation.
Let's say I have a dataframe, df with following structure.
A B C 1 1 7 5 3 3 3 3 2 7 5 2 5 NaN 2
We have 3 columns in the dataframe A, B & C.
B column consists of mean values wrt A.
Value of B in 3rd row (which is 3) is mean of first 3 rows of A (9/3) Similarly, value of B in 4th row = (Sum of values in 2nd,3rd and 4th row of A)/3
Now, let's say I have many NaN values in B and there are no NaN values in A, how do I write a function or code to fill the NaN values as per the logic discussed above?
I tried using loc and iloc but I guess I made some mistake.