Error in plotting a function, left and right side with diferent dimensions

When I use this code:

    format short
    
    prod_total = zeros(1000, 1);
    vet_pedidos = zeros(1000, 1);
    x_exp = zeros(1000, 1);
    vet_servido = zeros(1000, 1);
    for j = 1:1000
        a = rng_cheap;
        x = a;
        
        if (x <= 0.2)
            prod = 1;
        elseif (x > 0.2 &&  x <= 0.6)
            prod = 2;
        elseif (x > 0.6 && x <= 1)
            prod = 3;
        end
        prod_total(j) = prod;
        
        %
        y = 2.8*a + 0.8;
        y = y*10;
        y = fix(y);
        y = y/10;
        vet_pedidos(j)= y;
        %
        x_exp(j) = a;
        vet_servido(j) = - (1/2) * log(1- x_exp);
    end
    
    [xs, index] = sort(x_total);
    ys = vet_total(index);
    
    plot(xs, ys, '-x');
    

It gives me the following error:

    Unable to perform assignment because the left and right sides have a different number of elements.
    
    Error in enunciado8 (line 28)
    vet_servido(j) = - (1/2) * log(1- x_exp);
    

Context: the rng_cheap gives a number.

Answer 1

[Torsten]

Most probably,

vet_servido(j) = - (1/2) * log(1- x_exp(j));

instead of

vet_servido(j) = - (1/2) * log(1- x_exp);