Re: Re: Placeholders in matrix notation

• To: mathgroup at smc.vnet.net
• Subject: [mg29930] Re: [mg29899] Re: Placeholders in matrix notation
• From: "Hugh Philipp" <hph at com.dtu.dk>
• Date: Thu, 19 Jul 2001 03:56:56 -0400 (EDT)
• Organization: Reserach Center COM - DTU
• References: <9j0hhl\$fjn\$1@smc.vnet.net> <200107180608.CAA18930@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Can anybody think of a way to define a non-commutative differential operator
that you can just plug into matrix equations?
Perhaps the problem might be that the matrix routines assume that things
commute...

There is always a work around, but it would be nice to just say - 'Here is
my operator. Here are my hairy matrix expressions. Go tell me how everything
comes out.'  and - do this making it look as close to the stuff I scratch on
a back of an envelope as possible.

-Hugh.

----- Original Message -----
From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
To: mathgroup at smc.vnet.net
Subject: [mg29930] [mg29899] Re: Placeholders in matrix notation

> Hmm,
>
> perhaps because {D[#,x],0} is an operator ?
> and it has nothing to do with an dot product but
>
> Inner[#1[#2] &, {D[#, x] &, 0*# &}, {f[x], g[x]}]
>
> will work.
>
> Regards
>   Jens
>
> "Douglas F." wrote:
> >
> > I want to use the partial differential operator in matrix algebra. The
function
> > it operates on would be in another matrix.
> >
> > Here, I am using "d" to represent the partial operator
> > {esc}pd{esc}{ctrl-_}x{ctrl-space}
> >
> > [d   0] . Transpose[  f[x]|   g[x]  ]
> >
> > But Mathematica won't let me do the matrix multiplication. How do you do
that?
> >
> > -D

```

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