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Re: Matrix Manipulation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg16461] Re: [mg16389] Matrix Manipulation
  • From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
  • Date: Sat, 13 Mar 1999 02:22:00 -0500
  • Sender: owner-wri-mathgroup at wolfram.com

Here is one easy way do to this. First create the zero 3X3 matrix:
In[34]:=
A=Array[0&,{3,3}];

Next replace the the corresponding part of A by msub:

In[35]:=
A[[{1,3},{1,3}]]=msub;

Now you can simply add A to mm to get what you wanted:

In[36]:=
mm+A
Out[36]//MatrixForm=
22   2    25

4    5    6

30   8    33



On Thu, Mar 11, 1999, Andreas Paul Friedrich Bernhard <bernhard at eng.umd.e
du> wrote:


>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
>
>
>Thanks
>AndyIII
>
>--
>                                -------
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>Man would die from great loneliness of Spirit.
>For whatever happens to the beasts, soon happens to man. - Chief Seattle
>                                -------
>
>****************************************************
>*   Andreas P.F. Bernhard                          *
>*   Aerospace Department, University of Maryland   *
>*   College Park, MD 20742                         *
>*   bernhard at Glue.umd.edu                          *
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>****************************************************
>
>
>


Andrzej Kozlowski
Toyama International University
JAPAN
http://sigma.tuins.ac.jp/
http://eri2.tuins.ac.jp/



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