how can i solve an EDF?

How can i solve an equation having this form with Matlab : dy+y(t-h)=0 and plotting it's variation on the time with différents values of h .(h is a constant)

Answer 1

[Mischa Kim]

Triki, use one of the numerical integrators, e.g. ode45

 function ODEsim()
 tspan  = 0:0.1:10;                    % set up the problem
 IC     = 1;
 h      = 0.5;
 [t,yt] = ode45(@myODE,tspan,IC,[],h); % call the integrator
 plot(t,yt,'r')                        % plot the result
 xlabel('t')
 ylabel('y')
 grid
 end

 function dy = myODE(t,y,h)            % define the DE
 dy = -y*(t - h);
 end

[Mischa Kim]

Ok, I see.

 function DDEsim()
 h   = 1;
 lag = h;
 sol = dde23(@DDEeq,lag,@DDEhist,[0,5]);
 plot(sol.x,sol.y);
 xlabel('t');
 ylabel('y');
 end

 function dydt = DDEeq(t,y,Z)
 ylag = Z(:,1);
 dydt = -ylag;
 end

 function S = DDEhist(t)
 S = 1;
 end

Check out the DDE documatation for more detail.

Answer 2

[triki]

Thank you for your help,but there is a little mistake,witch is my edf is not dy=y*(t-h) but dy=y(t-h). That's mean that y in the second member dependent on t-h not multiplied by (t-h);in other way we can suppose a x=t-h so our equation become: dy/d(x+h)=-y(x)

[Mischa Kim]

Please add follow-up questions and comments as comments, not answers.