Re: System of ODE
- To: mathgroup at smc.vnet.net
- Subject: [mg41978] Re: [mg41960] System of ODE
- From: Selwyn Hollis <selwynh at earthlink.net>
- Date: Mon, 16 Jun 2003 03:56:25 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
NDSolve doesn't understand equations in matrix form, primarily because
Equal isn't Listable.
Here's the form you need:
NDSolve[Flatten[Thread /@ {A'[t] == M[t].A[t] + 2*C, A[0] == {0, 0}}],
A[t], {t, 0, 300}]
Note that you can't use D as a variable name, and matrix multiplication
is done with Dot, not *. And with such a long time interval, you'll
likely need to use the MaxSteps option.
-----
Selwyn Hollis
http://www.math.armstrong.edu/faculty/hollis
On Wednesday, June 11, 2003, at 01:17 PM, Amedeo wrote:
> Hello everyone....
> I want to solve a sytem of ordinary differential equation....the
> coefficent
> of this system are Matrices....I try to find in help but I don't find
> any
> result....
>
> the system is in this form
>
> A'[t] = D[t]*A[t]+2*C with a initial condition A[0] = {0,0}
> and t's gap {t,0,300}
>
> I try to write this with NDSolve but it return me a error
> NDSolve[{A'[t] = D[t]*A[t]+2*C,A[0] = {0,0}},A,{t,0,300}]
>
> Naturally D[t] is a matrix 2x2 and C is a columm of 2 element
>
> the dimension of matric D and C are ok
> but i don't know if i should declare A[t] as a variable matrices....
>
> the error that return NDSolve is
>
> NDSolve::deql : The First argument must have both an equation and an
> initial
> condition.
>
> thanx for help
> --
> AMS
> Michelin@ingegneriaPOINTunimePOINTit
>
>
>