Based on number of output values, how do I calculate the compound interest in Google Spreadsheet

Question

I have a spreadsheet with values in columns like a1:100 b1:200 c1:300 d1:400

Lets say these are values for Jan,Feb,Mar,April

I want to find out at what single monthly compound interest rate, the value of a1 reaches c1 or d1. I know that simple interest rate is 100% per month in the given example. But how do I find the compound interest rate in Google Spreadsheet knowing the output values over many months?

[I need to find value of i in the formula in google spreadsheet, given values of F, P, i] Here i is the compound interest, P is initial amount, F the final amount. n is the number of months.

F = P ( 1+i )^n

Answer 1

Found the solution offline through a friend. In the given example in Q statement, if I had to find the monthly compound interest for final value d1 starting from a1, it would be (in google spreadsheet)

=pow(D1/A1,1/(count(D1:A1)-1)) - 1