How can store the values of this forever-while loop?

clear all;clc;
N=1;
SI= exp(-1.*N);
tol = 10.^(-1.*10);
y = zeros(1,24)';
while 1,
    SI= exp(-1.*N);
    y = SI + rand;
    if SI<=tol
        break;
    end
    N=N+1;
end
xk= SI;
k=0:10:50;

Answer 1

[per isakson]

Try

clear all;clc;
N=1;
SI= exp(-1.*N);
tol = 10.^(-1.*10);
y = zeros(1,0);
while true
    SI= exp(-1.*N);
    y(1,end+1) = SI + rand;
    if SI<=tol
        break;
    end
    N=N+1;
end
xk= SI;
k=0:10:50;
y

it outputs

y =
  Columns 1 through 9
    1.1822    0.3789    0.9791    0.3683    0.2033    0.2536    0.6170    0.4736    
  .....

[Ruten9]

It worked! Thanks!