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

• To: mathgroup at smc.vnet.net
• Subject: [mg110380] Re: How to construct symmetric matrix from just a one half matrix
• From: Peter Breitfeld <phbrf at t-online.de>
• Date: Wed, 16 Jun 2010 05:37:18 -0400 (EDT)
• References: <hv76li$k4j$1@smc.vnet.net>

dragec 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
>

If we call your initial matrix hm, then

hm+Transpose[hm]-DiagonalMatrix[Diagonal[hm]]

will work

//Peter

-- 
_________________________________________________________________
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de