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Re: Merge of Matrices

  • To: mathgroup at smc.vnet.net
  • Subject: [mg71181] Re: Merge of Matrices
  • From: Bill Rowe <readnewsciv at sbcglobal.net>
  • Date: Thu, 9 Nov 2006 03:41:38 -0500 (EST)

On 11/8/06 at 6:15 AM, rberger06 at sinh.us (Robert Berger) wrote:

>I like to create from the four matrices A (N1 rows and N1 columns),
>B (N1 rows and N2 columns), C (N2 rows and N1 columns), D (N2 rows
>and N2 columns) a new matrix X of the form

>A  B
>X =
>C  D
>

>Once A & B and C & D have been merged, the first (A & B) and the
>second row (C& D) can be merged in that way by applying Join, which
>is not a problem but how can I merge A & B (and of course C & D) in
>that way?

Take a look at the functions AppendColumns and AppendRows in the 
package LinearAlgebra`MatrixManipulation`. Or if you prefer to 
"roll your own"

Joining A, B first can be done by

Transpose[Join@@(Transpose/@{A,B})]

or

MapThread[Join@@{##}&,{A,B}]

Similarly with C,D

Then the two intermediate matrices can be combined using either 
Join or Append to get the desired result.
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