How do I evaluate a function that contain an array index inside a sum?

I want to evaluate this function and save the result in an array in MATLAB

Where A and B are arrays, and N and P are constants. For example A = [1,2,3,4], B = [1,2,3], P = 6, and N = 4.

Also, I want to save the output of f(x) and its corresponding x value.

Answer 1

[Walter Roberson]

Calculate definite vector values and sum()

k = (1 : N-1) .';
f = @(x) A0/2 + sum(A(k) .* cos(2*pi.*k.*x./P) + B(k) .* sin(2*pi*.k.*x./P),1) + A(N).*cos(2*pi.*N.*x/P)/2

For example A = [1,2,3,4], B = [1,2,3], P = 6, and N = 12

N cannot be greater than one less than length(A) or length(B).

Also, unless you store in a separate variable like I used here, then you would need to make adjustments to the code to deal with the question of whether you are using 0-based indexing or 1-based indexing.

Note: this version of the code is vectorized, provided that x is a row vector.