MATLAB: Am I doing this right? (a Math formula to Matlab language)

Question

I needed to calculate this formula:

So I wrote a function in order to do that:

(P is x and P^ is y):

function NS = nash_sat(x, y)
% This function calculates Nash-Sutcliffe efficiency coefficient
%   Detailed explanation goes here
A = sum (x-y).^2;
B = sum (x-(mean(x)).^2;
fraction = (A/B);
NS = 1-fraction;
end

This is the first time I type a math formula in Matlab. I want to know if I typed the formula in the function correctly or not.

Thank you so much.

Answer 1

You are on the right track, but have typos in the code due to parentheses issues.

A = sum( (x - y).^2 );
B = sum( (x - mean(x)).^2 );