"Index exceeds the number of array elements (2)" when it shouldn't?

So Matlab shows an error in line 11 even though both vectors are defined and should have the exact same length of 45000.

Does anyone know where the problem lies?

I would be beyond grateful for your help!

function seq = problem_phone_2( y )
y = y.';
y = y - mean(y);
l = length(y);
%n = 2^nextpow2(l);
j = 1;
seq = zeros(1, 5);
for p = 1:5
    a = zeros(l, 1);
    for k = (((j - 1)*5000) + 1):(j*5000)
        a(k) = y(k);
    end
    f = fft(a, l);
    f = abs(f)/5000;
    j = j + 2;
    f1 = f(1:45000/2);
    ind = f1 > 0.15;
    f1 = ind.*f1;
    [m,n] = findpeaks(f1);
    y = n.*50/45;
    if (y(1) + y(2)) - 1906 < 3
        seq(p) = 1;
    elseif (y(1) + y(2)) - 2033 < 3
        seq(p) = 2;
    elseif (y(1) + y(2)) - 2174 < 3
        seq(p) = 3;
    elseif (y(1) + y(2)) - 1979 < 3
        seq(p) = 4;
    elseif (y(1) + y(2)) - 2106 < 3
        seq(p) = 5;
    elseif (y(1) + y(2)) - 2247 < 3
        seq(p) = 6;
    elseif (y(1) + y(2)) - 2061 < 3
        seq(p) = 7;
    elseif (y(1) + y(2)) - 2188 < 3
        seq(p) = 8;
    elseif (y(1) + y(2)) - 2329 < 3
        seq(p) = 9;
    elseif (y(1) + y(2)) - 2277 < 3
        seq(p) = 0;
    end
end
end

Answer 1

[Adam Danz]

It looks like this

for k = (((j - 1)*5000) + 1):(j*5000)

a(k) = y(k);

end

could be replaced with

k = (((j - 1)*5000) + 1):(j*5000);

a = y(k);

And since this function assumes y has 45000 elements, you should add a test to the top of the function,

assert(numel(y)==45000, 'Y should have 45000 elements.')