octave error: subscript indices must be either positive integers or logicals

Question

I'm trying to sum the product of an indexed vector and an indexed matrix like this:

k=[0:1:N-1]  
n=[0:1:N-1]  
x_n = sin(pi*n)  
N = size(x_n,2)  
_seqgen(x_n(n)*exp(k*n/N), n, 0..N-1)  

but I get the error:

error: subscript indices must be either positive integers or logicals  

What am I missing here?

EDIT: I just realized that I missed the _plus function to sum the generated sequences. It should look like this:

k=[0:1:N-1]  
n=[0:1:N-1]  
x_n = sin(pi*n)  
N = size(x_n,2)  
_plus(_seqgen(x_n(n)*exp(k*n/N), n, 0..N-1))  

I still get the same error though...

Answer 1

The error message explains what is wrong: you are trying to index an array with a number which is not a positive integer or logical. The only array indexing in your code is x_n(n). And sure enough, the line n=[0:1:N-1] demonstrates that the index n is not positive, since 0 is not a positive number. Lesson: MATLAB/Octave always index from 1. I do suggest you real some tutorials as this is fundamental stuff which you'll need to know.