pandas dataframe computation between columns

Question

I have a panda dataframe. Given two columns, I'd like to compute the following

(sum(xy) - sum(x)*sum(y)/n)^2

Here x is an element in the first column, y is the corresponding element in the second column, and n is the length of the column.

I'd like to compute the above between df.column[0] and every other column. Then I would like to get the column index that corresponds to the smallest value.

Answer 1

这样的事情可能是？

((df['x'] * df['y']).sum() - df['x'].sum() * df['y'].mean()) ** 2