Storing column vectors over a while loop

Hi I'm having problems with my code. When it goes to the second while loop it does not record the values(.i.e it stops giving me the error that array position values most be logical or positive integers). Any hints on how to solve this?

N = 100
B = [-30 -10 0 0; -10 -30 -10 0; 0 -10 -30 -10; 0 0 -10 -30];
h = 50/2N ;
n = 1;
x = zeros(4,10/h);
x(:,1) = [1;0;0;1];
euclidean_norm(n) = 0;
time(n) = 0;
time_end = 10;
while n<=3
    time(n+1) = time(n)+h;
    x(:,n+1) = x(:,n) + h*B*x(:,n);
    euclidean_norm(n+1) = norm(x(:,n));
    n=n+1;
end
while time(n)+h < time_end + eps(1)
    time(n+1) = time(n)+h;
    x(:,n+1) = x(:,n) + h((23/12)*B*x(:,n)-(16/12)*B*x(:,n-1)+(5/12)*B*x(:,n-2));
    euclidean_norm(n+1) = euclidean_norm(x(:,n+1));
    n = n + 1;
end
plot(time(1:n),euclidean_norm(1:n))

Answer 1

[David Hill]

N = 100;
B = [-30 -10 0 0; -10 -30 -10 0; 0 -10 -30 -10; 0 0 -10 -30];
h = 50/(2*N);%I believe this is what you wanted.
n = 1;
x = zeros(4,10/h);
x(:,1) = [1;0;0;1];
euclidean_norm(n) = 0;
time(n) = 0;
time_end = 10;
while n<=3
    time(n+1) = time(n)+h;
    x(:,n+1) = x(:,n) + h*B*x(:,n);
    euclidean_norm(n+1) = norm(x(:,n));
    n=n+1;
end
while time(n)+h < time_end + eps(1)
    time(n+1) = time(n)+h;
    x(:,n+1) = x(:,n) + h*((23/12)*B*x(:,n)-(16/12)*B*x(:,n-1)+(5/12)*B*x(:,n-2));%Need h*
    euclidean_norm(n+1) = norm(x(:,n+1));%I believe you want norm(x(:,n+1)) instead of euclidean_norm which causes error.
    n = n + 1;
end
plot(time(1:n),euclidean_norm(1:n))