Help with indexing error

function B = Ecomp(e,f)
%Compares 2 elements of equal length (unfactored) in
%Sn and sees if theyre the same, i.e cyclic permutations of each other.
B='TRUE';
k=0;
n=length(e);
for i = 1:n
    if f(i) == e(1)
        k=i;
    end
end
    for j = 1:n-1
        if f(mod(k+j,n)) ~= e(j+1) 
            B='FALSE';
            return
        end
    end
end

This function is supposed to compare two vectors and see if they are cyclic permutations of each other. For example, Ecomp([1,2,3,4],[4,1,2,3]), should return 'TRUE', however when I input this the error that I get is:

>> Ecomp([1,2,3,4],[4,1,2,3])
Subscript indices must either be real positive integers or logicals.

Error in Ecomp (line 13)
        if f(mod(k+j,n)) ~= e(j+1)

I can't see why as my indexing starts from 1, any help much appreciated.

Answer 1

[Walter Roberson]

mod() can return 0.