MathGroup Archive 2003

[Date Index] [Thread Index] [Author Index]

Search the Archive

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
>
>
>


  • Prev by Date: Re: Averaging
  • Next by Date: Re: InverseFunction[]
  • Previous by thread: Re: System of ODE
  • Next by thread: Re: System of ODE