Index exceeds the number of array elements. Index must not exceed 0. Help with debugging.

I just can't figure out what's wrong with the loop that this error occurs:

Index exceeds the number of array elements. Index must not exceed 0.

n_even=2:2:10;
x=1:10;
for j=1:length(n_even)
    for k=1:length(x)
        y(k)=8+4.*cos(x(k));
        [h_simp(j,k),I1_simp(j,k)]=simpson13(@(x) 8+4.*cos(x(k)),0,y(k),n_even(j));
    end
end

[Walter Roberson]

I suspect the error is inside simpson13

[Torsten]

@(x) 8+4.*cos(x(k))

I doubt that "simpson13" calls the function with a vector of changing length for x.

[Walter Roberson]

But simpson13 might, for example, be written in terms of global variables... that are not initialized.

[Walter Roberson]

You can see from this experiment that the overall framework does not give the indexing error, so the problem must be in simpson13

simpson13 = @(f, p, q, r) deal(randi(9), randi(9));

n_even=2:2:10;
x=1:10;
for j=1:length(n_even)
    for k=1:length(x)
        y(k)=8+4.*cos(x(k));
        [h_simp(j,k),I1_simp(j,k)]=simpson13(@(x) 8+4.*cos(x(k)),0,y(k),n_even(j));
    end
end

h_simp

h_simp = 5×10

5 1 1 4 5 8 2 2 4 6 8 3 9 8 2 6 6 9 2 5 3 7 9 9 3 6 7 3 9 7 5 7 9 8 1 8 2 7 3 9 6 6 5 7 4 6 7 9 5 1

[Efrat Hazan Elimelech]

Ok that’s interesting… I guess you get the same dimensions matrice when you print the I1_simp.