Plot line doesn't follow function

The plot line I created doesn't follow the function, which should be an exponencial.

The following code, only the final for loop matters to the question:

format short

prod_total = [];

for j = 1:1000
    x0 = 4;
    m = 5;
    vetor_aleatorio = [ ];
    for k = 1:100
        [u1, x0] = n_aleatorio(x0, k, m);
        vetor_aleatorio(k) = u1;
    end
    
    x = rand;
    
    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 = [prod_total, prod]; 
    
end

Unrecognized function or variable 'n_aleatorio'.

histogram(prod_total)

y = 2.8*rand + 0.8;
y = y*10;
y = fix(y);
y = y/10;
vet_pedidos(i)=y;


vet_servido = [];

x_total = [];
vet_total = [];
for i = 1:1000
    x_exp = rand;
    vet_servido = - (1/2) * log(1- x_exp);
    vet_total = [vet_total, vet_servido];
    x_total = [x_total, x_exp];
end

plot(x_total, vet_total, '-x');

[Matt J]

Your code does not run (see above).

[Pedro Almeida]

Yeah you are right, just use this:

for i = 1:1000
        x_exp = rand;
        vet_servido = - (1/2) * log(1- x_exp);
        vet_total = [vet_total, vet_servido];
        x_total = [x_total, x_exp];
    end
    plot(x_total, vet_total, '-x');
    
    

Answer 1

[Jan]

You determine the corret values, but draw them in random order. Sorting cleans the diagonalish lines:

x_total   = zeros(1, 1000);  % Pre-allocation for speed
vet_total = zeros(1, 1000);  % Pre-allocation for speed
for i = 1:1000
    x_exp = rand;
    vet_servido  = - (1/2) * log(1- x_exp);
    vet_total(i) = vet_servido;
    x_total(i)   = x_exp;
end

[xs, index] = sort(x_total);
ys = vet_total(index);
plot(xs, ys, '-x');