Index exceeds matrix dimensions

I have written this code but keep getting the error "Index exceeds matrix dimensions"

x=5
N = 30
i = 1 : N;
k = 5-i+(N-3);
y = 2 .* k(1:N-2) .* x(i(1:N-2)+1) + 3 .* x(i(1:N-2)-1);

Answer 1

[Walter Roberson]

Your original equation

y=2k*x(i+1)+3*x(i-1)

implies that x is a vector being indexed at i+1 and i-1.

Your current code has

x = 5;

which is a scalar. You cannot index a scalar at anything other than [] or 1 or true or false.

If your original code was intended to represent multiplication rather than indexing then:

y = 2 .* k(1:N-2) .* x .* (i(1:N-2)+1) + 3 .* x .* (i(1:N-2)-1);