How can I save internal variable to a vector with ode45.

function [dx]= system(t,x)
global m I
F= expression;
u=F+alpha*u(t-1);

dx(1)=x(2);
dx(2)=m*x(1)+u/I;
dx(3)=-m*x(1)-u/I; 
dx=[dx(1);dx(2);dx(3)]';
end

[time,Xs]=ode45(@system(t,x),[0:0.1: 7],x01)
x01=[0.05 0.05 0 ]'

I want to save u , and use it to have u(t-1)

[Stephen23]

Use a nested function.

[Jan]

How should this work at the initial t?