augcoefmatrix and linsolve



On 5/17/07, Wolfgang Lindner <LindnerW at t-online.de> wrote:
>
> given a   m x n-matrix e.g.
> A: [1  1 -2]
>     [1 -1 -3]
>
> I want to automatic construct the right 'input'list [x+y=2,x-y=3]


The easiest way is probably:

Meq: A . [x,y,1]
      => matrix([y+x-2],[-y+x+3])

To extract the equations, you can use maplist(first,Meq) or
transpose(Meq)[1] or makelist(Meq[i,1],i,1,2).

For linsolve and the other solve functions, the equation x=y is entirely
equivalent to x-y (implicitly x-y=0).  If for some reason you want explicit
equations, I suppose you could do

   A . [x,y,0]  and A . [0,0,1]

to extract the left- and right-hand sides separately.

           -s