Re: Re: Creating a symmetric matrix

*To*: mathgroup at smc.vnet.net*Subject*: [mg46876] Re: [mg46857] Re: [mg46853] Creating a symmetric matrix*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Fri, 12 Mar 2004 23:39:22 -0500 (EST)*References*: <200403110850.DAA13986@smc.vnet.net> <200403120702.CAA25478@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

It seems that I was the only one who thinks that a "triangular matrix" is a "strick triangular matrix", that is with zeros on the diagonal. had I not made this assumption I would have suggested: A+Transpose[A]*Array[KroneckerDelta[#1 != #2,True]&,Dimensions[A]] Andrzej On 12 Mar 2004, at 08:02, Andrzej Kozlowski wrote: > > On 11 Mar 2004, at 09:50, Mark Coleman wrote: > >> Greetings, >> >> How can I efficiently build a symmetric matrix from an upper >> triangular >> one, i.e., extract the upper triangular elements and insert them into >> the lower triangle in such a way as to make the resulting square >> matrix >> symmetric? >> >> Thanks, >> >> Mark >> >> >> > > The most natural way must be > > A+Tranpose[A] > > e.g. > > A = Array[KroneckerDelta[#1 < #2, True] & , {3, 3}]; > > > {{0, 1, 1}, {0, 0, 1}, {0, 0, 0}} > > > A + Transpose[A] > > > {{0, 1, 1}, {1, 0, 1}, {1, 1, 0}} > > > > Andrzej Kozlowski > Chiba, Japan > http://www.mimuw.edu.pl/~akoz/ > >

**Follow-Ups**:**Re: Re: Re: Creating a symmetric matrix***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>

**References**:**Creating a symmetric matrix***From:*Mark Coleman <mark@markscoleman.com>

**Re: Creating a symmetric matrix***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>