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

• To: mathgroup at smc.vnet.net
• Subject: [mg110399] Re: How to construct symmetric matrix from just a one half matrix
• From: Simon <simonjtyler at gmail.com>
• Date: Wed, 16 Jun 2010 05:40:56 -0400 (EDT)
• References: <hv76li\$k4j\$1@smc.vnet.net>

Here's a couple of ways...

half=ImportString["1  0  0  0
2  3  0  0
4  9  5  0
2  2  3  4","Table"];

half+half\[Transpose]-DiagonalMatrix[Diagonal[half]]
(1	2	4	2
2	3	9	2
4	9	5	3
2	2	3	4)

In:= Array[half[[Sequence@@Sort[{#1,#2},Greater]]]&,{1,1}
Length[half]]
(1	2	4	2
2	3	9	2
4	9	5	3
2	2	3	4)

On Jun 15, 4:30 pm, dragec <culino... at gmail.com> wrote:
> 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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