Replacing Part of a Matrix

• To: mathgroup at smc.vnet.net
• Subject: [mg20250] Replacing Part of a Matrix
• From: flippy652 at my-deja.com
• Date: Fri, 8 Oct 1999 18:30:22 -0400
• Sender: owner-wri-mathgroup at wolfram.com

Hello all,

I have a n x n matrix, call it A.

I have a (n - 2)x(n - 2) matrix, call it B.

I would like to keep the outer rows and columns
of A, but repalce the inner rows and columns with
thos of B to get a new C.

I looked at the ReplacePart and other matrix and
list manipulation rules and couldn't quite find
one.

I wrote a very gross module to do it.

Does anyone have such a module in Mathematica they would
like to share.

For example,

c = replace_a_b[a, b]

would return the desired result.

Example:

A = {{1,2,3,4},{5,6,7,8},{9,10,11,12},
{13,14,15,16}}
B = {{20,30,},{40,50}}

C = replace_a_b[A,B], would produce:

C = {{1,2,3,4},{5,20,30,8},{9,40,50,12},
{13,14,15,16}}

Basically, this function just replaces the
interior (n-2)x(n-2) in the larger matrix.

Can anyone help?

By the way, thank you to all who responded with
such an easy and useful rectangular grid
generator.

Thank you.

Wilson Figueroa
flip at safebunch.com
http://safebunch.com

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