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Re: How to construct symmetric matrix from just a one half matrix

  • To: mathgroup at smc.vnet.net
  • Subject: [mg110411] Re: How to construct symmetric matrix from just a one half matrix
  • From: "Hans Michel" <hmichel at cox.net>
  • Date: Wed, 16 Jun 2010 05:48:26 -0400 (EDT)
  • References: <hv76li$k4j$1@smc.vnet.net>

I think you may want to try

In[1]:= 
ma=SparseArray[{Band[{1,1}]->{1,3,5,4},Band[{2,1}]->{2,9,3},Band[{3,1}]->{4,2},Band[{4,1}]->{2}},{4,4}]
Out[1]= SparseArray[<10>,{4,4}]
In[2]:= (ma-(IdentityMatrix[4] Diagonal[ma])+Transpose[ma])//MatrixForm
Out[2]//MatrixForm= (1 2 4 2
2 3 9 2
4 9 5 3
2 2 3 4

)
Hans
"dragec" <culinovic at gmail.com> wrote in message 
news:hv76li$k4j$1 at smc.vnet.net...
> please help me with simple to apply function that will construct
> symmetric matrix from given just a half matrix with diagonal.
> Eg:
>
> From:
> 1  0  0  0
> 2  3  0  0
> 4  9  5  0
> 2  2  3  4
>
> To give:
>
> 1  2  4  2
> 2  3  9  2
> 4  9  5  3
> 2  2  3  4
> 



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