Jens,
Does the following Sage command-line session begin to do what you
want?
Various parts could be more streamlined and/or automated for a larger
matrix.
Rob
sage: for i in range(4):
....: var("a"+str(i))
....:
a0
a1
a2
a3
sage: J = matrix(2,2,[a0,a1,a2,a3])
sage: J
[a0 a1]
[a2 a3]
sage: K = J.subs(a2=17)
sage: K
[a0 a1]
[17 a3]
On Jun 22, 3:05 am, Jens <jens.put...@gmail.com> wrote:
> Hello,
>
> I try to define a matrix (in particular a skew symmetric) with some
> variables as entries. I know how to do it by hand defining some
> variables and then put then into a matrix but what I want to have
> seems to more complicated.
>
> 1. I choose a size for the 2g x 2g matrix say g=2
> 2. I want to generate a matrix J
> [0,a1,a2,a3]
> [-a1,0,a4,a5]
> [-a2,-a4,0,a6]
> [-a3,-a5,-a6,0]
>
> It would be perfect if there is the possibility that i can work with
> the ai and if further calculations lead to
>
> a1=1
>
> J is changed.
>
> I had the idea to generate a kind of list/vector where the entries are
> stored first symbolic variables which can be set step by step to some
> value. It is something like the matrix with values that are somehow
> linked to that list.
>
> I need the variables because they has to fulfill some conditions.
>
> Thanks
>
> Jens
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