Re: Define a matrix function with size as argument

• To: mathgroup at smc.vnet.net
• Subject: [mg71372] Re: Define a matrix function with size as argument
• From: "Simone Giannerini" <sgiannerini at gmail.com>
• Date: Thu, 16 Nov 2006 00:52:55 -0500 (EST)
• References: <ejf10f\$4pt\$1@smc.vnet.net> <455B1696.2080200@metrohm.ch>

```Dear All,

ciao

Simone

On 11/15/06, dh <dh at metrohm.ch> wrote:
> Hi Simone,
> you wrapped MatrixForm[...] around your matrix. Therefore, this will not
> be recognized as a matrix. Simply remove MatrixForm and everything works
> as expected.
> Daniel
>
> Simone Giannerini wrote:
> > Dear all,
> >
> > I am quite new to Mathematica and I have the following problem I could
> > not find track of both in the Forum and in the documentation.
> > I need to define a matrix function with size of the matrix as an
> > argument. The function produces a tridiagonal matrix:
> >
> > Q[w_] := MatrixForm[SparseArray[
> >     {i_, j_} /; Abs[i - j] <= 1 -> Which[i < j,
> >       a[i - 1]*(1 - (i - 1)/(2*w)), i > j,
> >       (a[-i + 2*w + 1]*(i - 1))/(2*w), i == j,
> >       (-(1 - (i - 1)/(2*w)))*a[i - 1] -
> >        (a[-i + 2*w + 1]*(i - 1))/(2*w) + 1],
> >     {2*w, 2*w}]]
> >
> >
> > dum = Q[2]
> >
> > the problem is that dum is not recognized as a matrix so that
> > operations like Inversion and the like do not work.
> >
> > Many thanks for your attention.
> >
> > Kind regards,
> > ______________________________________________________
> >
> > Simone Giannerini
> > Dipartimento di Scienze Statistiche "Paolo Fortunati"
> > Universita' di Bologna
> > Via delle belle arti 41 - 40126  Bologna,  ITALY
> > Tel: +39 051 2098262  Fax: +39 051 232153
> > ______________________________________________________
> >
>
>

--
______________________________________________________

Simone Giannerini
Dipartimento di Scienze Statistiche "Paolo Fortunati"
Universita' di Bologna
Via delle belle arti 41 - 40126  Bologna,  ITALY
Tel: +39 051 2098262  Fax: +39 051 232153
______________________________________________________

```

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