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From: kaledh Dickinson on 9 Mar 2010 05:35
hi all,

I have a problem using dde23 solver to evaluate the delayed HR model:


dx/dt = y(t) - a*x(t)^3 + b*x(t)^2 - z(t) + e (x(t-tau) - x(t))

dy/dt = c - d*x(t)^2 - y(t)

dz/dt = r [ s*(x(t) - xo) - z(t)]


how could I set the history values?

it is possible use the dde23 solver or I must use some approximation? if so what's the best approximation method?

please help me.
tnx


From: kaledh Dickinson on 10 Mar 2010 10:41
nobody?
From: Torsten Hennig on 10 Mar 2010 01:36
> hi all,
>
> I have a problem using dde23 solver to evaluate the
> delayed HR model:
>
>
> dx/dt = y(t) - a*x(t)^3 + b*x(t)^2 - z(t) + e
> (x(t-tau) - x(t))
>
> dy/dt = c - d*x(t)^2 - y(t)
>
> dz/dt = r [ s*(x(t) - xo) - z(t)]
>
>
> how could I set the history values?
>

If you mean technically in MATLAB:

function yhistory = history(t)
%yhistory returns a vector with values for x,y and z
%for t<= tstart
yhistory = [... ... ...];

If you mean:
according to the HR model:
I don't know.

> it is possible use the dde23 solver or I must use
> some approximation? if so what's the best
> approximation method?
>

It is possible to use dde23 if tau is constant.

> please help me.
> tnx
>
>

Best wishes
Torsten.
From: kaledh Dickinson on 12 Mar 2010 12:36
Torsten Hennig <Torsten.Hennig(a)umsicht.fhg.de> wrote in message <1151130767.357305.1268238994600.JavaMail.root(a)gallium.mathforum.org>...
> > hi all,
> >
> > I have a problem using dde23 solver to evaluate the
> > delayed HR model:
> >
> >
> > dx/dt = y(t) - a*x(t)^3 + b*x(t)^2 - z(t) + e
> > (x(t-tau) - x(t))
> >
> > dy/dt = c - d*x(t)^2 - y(t)
> >
> > dz/dt = r [ s*(x(t) - xo) - z(t)]
> >
> >
> > how could I set the history values?
> >
>
> If you mean technically in MATLAB:
>
> function yhistory = history(t)
> %yhistory returns a vector with values for x,y and z
> %for t<= tstart
> yhistory = [... ... ...];
>
> If you mean:
> according to the HR model:
> I don't know.
>
> > it is possible use the dde23 solver or I must use
> > some approximation? if so what's the best
> > approximation method?
> >
>
> It is possible to use dde23 if tau is constant.
>
> > please help me.
> > tnx
> >
> >
>
> Best wishes
> Torsten.

thank you for the reply.

first of all tau is constant so I can use the dde23 but I need to calculate the history of the model.

Do you have any suggestion to calculate it (according with the HR model)?

tnx again
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