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Re: Matrix Manipulation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg16438] Re: Matrix Manipulation
  • From: "Allan Hayes" <hay at haystack.demon.co.uk>
  • Date: Sat, 13 Mar 1999 02:21:48 -0500
  • References: <7c5bl0$7rt@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Andreas Paul Friedrich Bernhard wrote in message
<7c5bl0$7rt at smc.vnet.net>...
>
>I am trying to modify the elements of a submatrix in a matrix, without
>having to replace each element explicitly
>
>for example:
>mm   = { {1,2,3}, {4,5,6}, {7,8,9} }
>msub      = { {21,22}, {23,24} }
>I now wish to add the sub matrix: to positions (1,1),(1,3),(3,1),(3,3)
>
>I have tried using ReplacePart but it does not recognize the
>multidimensional replacement, I have also tried
>mm[ {{1,3} , {1,3}} ]  = mm[ {{1,3} , {1,3}}]  + msub
>
>but this crashes horribly
>

Andy:

mm = { {1,2,3}, {4,5,6}, {7,8,9} };
msub = { {21,22}, {23,24} };

mm[[{1,3},{1,3}]] =msub;mm

{{21,2,22},{4,5,6},{23,8,24}}

---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565





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