For Loop (or if-condition) is ignoring the first value

Hello everybody, like I mentioned I´ve got the problem, that the first value is ignored (the first value of the matrix 'auftraege'):

for j=1:n_pop
    for i=1:n_auf*n_lkw
        for k=1:n_auf
            if matrix(j,i)==auftraege(k,1) 
                matrix(j,i)=auftraege(k,2);
            end
        end
    end
end

2 0 0 0 3 0 0 5 1 4

1 0 0 0 4 0 0 2 1 1

If I use this code and set k to k=2:n_auf I get the same solution as mentioned above.

for j=1:n_pop
    for i=1:n_auf*n_lkw
        for k=1:n_auf
            if matrix(j,i)==auftraege(1,1) 
                matrix(j,i)=auftraege(k,2);
            end
        end
    end
end

0 0 5 4 0 1 0 3 0 2

0 0 5 4 0 4 0 3 0 2

As you can see: When I put the number 1 directly into the if condition, the solution for the 1 is correctly. After these tests I think the problem is that the for loop starts with k=2 and not k=1. Do you think I´m right with my guessing? Or do you even got a solution?

Thanks everybody