MathGroup Archive 2001

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

Search the Archive

Re: SetDelayed problems with matrix operation


Hi,

but the right hand side is not evaluated and the symbolic
expression MatrixExp[A t].{b1,0,0} is a singel expression and
not a list of three expressions.

If you have a fixed value for t you can comput the vector on the
right hand side. 

You definition should be

x[i_Integer][t_?NumericQ]:=Part[MatrixExp[A t].{b1, 0, 0},i]

Regards
  Jens

"SANCHEZ DE LEON, Guillermo" wrote:
> 
> Given a square matrix such as
> 
> A={{-3, 0, 0.05}, {0.8, -0.01, 0}, {0, 0.01, -0.05}}
> 
> I wish evalute the expresion:
> 
> { x1[t_], x2[t_], x3[t_]} : = MatrixExp[A t].{b1, 0, 0}
> 
> I receive the message
> 
> SetDelayed::"shape": "Lists{ x1[t_], x2[t_], x3[t_] } and  MatrixExp[A t)] .
> {b1, 0, 0} are not the same shape."
> 
> But it is known that when MatrixExp[A t].{b1, 0, 0} will be evaluate , given
> a  value for t,  the solution  will be already a list of the same shape that
> Lists{ x1[t_], x2[t_], x3[t_]}
> 
> For instance:
> 
> MatrixExp[A t].{b1, 0, 0}/.t->3 it work fine.
> 
> How it will be build the the expresion { x1[t_], x2[t_], x3[t_]} : =
> MatrixExp[A t].{b1, 0, 0} to be evaluated?


  • Prev by Date: Chaos-to-order (cont'd)
  • Next by Date: Re: PALETTE
  • Previous by thread: Re: SetDelayed problems with matrix operation
  • Next by thread: J/Link