Problel with save ommande

I have a problem with the save command in this code

Warning Variable 'x' cannot saved to MAT-file whose version is older than 7.3

To save this variable, use the -v.3 switch

 t=0:0.1:1825;
  N=length(t);
x=zeros(N,N);
for n=2:N
      x(1,n)=1;
    for i=2:N
        z=RK4(t(n-1),t(n),2,x(i-1,n-1));
        x(i,n)=z(end);
        clear z
    end
end
save('x.mat','x');
clear x

Answer 1

[Walter Roberson]

Your x is 18251 elements long, so N = 18251 . You create your x array as N x N double precision, which is 18251 x 18251 x 8 bytes/entry = 2664792008 bytes, which is about 2.5 gigabytes.

MATLAB's -v7 default save format cannot save variables that are larger than 2 gigabytes.

You will need to use

save('x.mat', 'x', '-v7.3')

[B.E.]

Anthore question, the calculation time required is about . Is that normal?

Knowing that for , the calculation time is about

[Walter Roberson]

You should probably try vectorizing RK4