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Topic: Logistic equation with delay
Replies: 8   Last Post: Mar 24, 2014 3:42 AM

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Torsten

Posts: 1,457
Registered: 11/8/10
Re: Logistic equation with delay
Posted: Mar 21, 2014 8:57 AM
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"Adin" wrote in message <lghcg7$nqs$1@newscl01ah.mathworks.com>...
> "Torsten" wrote in message <lggr8s$dj8$1@newscl01ah.mathworks.com>...
> > "Adin" wrote in message <lggbgg$95h$1@newscl01ah.mathworks.com>...
> > > I am trying to solve a logistic equation with delay WITHOUT using dde23. So the delay is of the form: ddtN(t)=N(t)(a-bN(t-?t)),a>0,b>0
> > >
> > > I have a function called logistic that looks like this:
> > > function dN = logistic(t,N)
> > > global a b;
> > > dN = (a-N.*b)*N;
> > >
> > > And another file that calls this function with ode45 like this:
> > > global a b;
> > > a = 4;
> > > b = 1;
> > > [t, N] = ode45('logistic', [0:.01:5], 10);
> > >
> > >

> >
> > ok, here you try to solve the _continuous_ logistic equation without delay.
> >

> > > I think I understand how to write a for-loop to calculate the logistic equation with delay of 1 since I'm picking my ? to be 1; but I'm not getting the correct results. Here is the code:
> > > S=zeros(501,1);
> > > t=zeros(501,1);
> > > S(1)=0;
> > >
> > > for iterate=1:501
> > > S(i) = S(i-1) + r*S(i-1)*(1-b*S(i-1))
> > > end
> > > plot(t,S)
> > >

> >
> > ok, here you try to solve the _discrete_ logistic equation without delay (although the case S(1)=0 is not that interesting)
> >

> > >
> > > Any ideas?

> >
> > And where do you try to solve the continuous logistic equation with delay ?
> >
> > Best wishes
> > Torsten.

>
> Oh, I thought I was solving for the continuous logistic equation with delay on the last part but I guess not....what do I have to add/change to do that then?


You'll have to use dde23.

Best wishes
Torsten.



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