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RE: Matrix Expansion question to Mathgroup

  • To: mathgroup at
  • Subject: [mg47751] RE: [mg47738] Matrix Expansion question to Mathgroup
  • From: "DrBob" <drbob at>
  • Date: Sun, 25 Apr 2004 05:13:23 -0400 (EDT)
  • Sender: owner-wri-mathgroup at

It's a MODERATED group. That means, in this case, e-mails don't get posted
until Steven Christensen gets a chance to screen all the e-mails -- and
that's not his only task in life. Don't assume your e-mail didn't get
through just because you don't see it posted within six hours, or 24 for
that matter. It's well worth the wait, to avoid spam and
character-assassination getting on the list.


-----Original Message-----
From: Larry Caruso [mailto:lcaruso at] 
To: mathgroup at
Subject: [mg47751] [mg47738] Matrix Expansion question to Mathgroup

I emailed the Mathgroup submission request (below) yesterday, 4/22, but
since it did not appear in today's listing, I assume it was somehow trivial.
However, I've been unable to locate a similar question elsewhere. Can you
provide further guidance?

I have a large, square matrix where each m[[ i, j ]] is populated with f[ i,
j ],
which happens to be a list {dx, dy}. At some later date, having
collected more data, I want to expand matrix this to a larger square matrix
using the same f [ i, j ] without losing any previously stored information.
Since the matrix is huge, regenerating it takes far too long, so I want to
simply add on the new data. I've tried experimenting with AppendRows[] and
other routines, but they only operate on non-lists. As far as I can
determine, using a C compiler with Mathlink may be my only option where I'm
regenerating the matrix from scratch as quickly as possible instead of
adding only new data.

Are there any other reasonable possibilities? Thanks.

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