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Re: basic operations in matrices

  • To: mathgroup at smc.vnet.net
  • Subject: [mg34593] Re: [mg34542] basic operations in matrices
  • From: BobHanlon at aol.com
  • Date: Wed, 29 May 2002 02:44:57 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 5/27/02 2:24:48 AM, junkc at fh-trier.de writes:

>I'm new to Mathematica and I'm searching for an operation, that simply
>transpose two rows or columns of a matrix M.
>
>e.g:
>
>Operation[M,{1,3}]
>
>1 1 1 1             3 3 3 3
>2 2 2 2   --->     2 2 2 2
>3 3 3 3             1 1 1 1
>4 4 4 4             4 4 4 4
>
>Much thanks in advance,
>

swapRows[mat_List,
 
      {r1_Integer?Positive, r2_Integer?Positive}] :=
    
    ReplacePart[mat, mat, {{r1},{r2}}, {{r2},{r1}}] /;
 
      r1 <= Length[mat] && r2 <= Length[mat];

swapColumns[mat_List,
 
      {c1_Integer?Positive, c2_Integer?Positive}] :=
    
    Module[{t=Transpose[mat]},
        Transpose[ReplacePart[t, t, {{c1},{c2}}, {{c2},{c1}}]]] /;
 
      c1 <= Length[mat[[1]]] && c2 <= Length[mat[[1]]];

mat = Array[m,{4,4}];

swapRows[mat, {1,3}]

swapColumns[mat, {1,3}]

Bob Hanlon
Chantilly, VA  USA


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