Re: Creating a symmetric matrix

• To: mathgroup at smc.vnet.net
• Subject: [mg46870] Re: Creating a symmetric matrix
• From: Paul Abbott <paul at physics.uwa.edu.au>
• Date: Fri, 12 Mar 2004 02:21:50 -0500 (EST)
• Organization: The University of Western Australia
• References: <c2p9ld\$dns\$1@smc.vnet.net> <c2rne4\$p04\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```In article <c2rne4\$p04\$1 at smc.vnet.net>,
Jens-Peer Kuska <kuska at informatik.uni-leipzig.de> wrote:

> ll = PadRight[#, 4, 0] & /@ Table[a[j, i], {j, 1, 4}, {i, 1, j}];
> ll = ll + MapIndexed[If[Equal @@ #2, 0, #1] & , Transpose[ll], {2}]

ll = PadRight[#, 4, 0] & /@ Table[a[j, i], {j, 1, 4}, {i, 1, j}];

ll + Transpose[ll] - DiagonalMatrix[Tr[ll, List]]

Cheers,
Paul

> Regards
>   Jens
>
> 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
>

--
Paul Abbott                                   Phone: +61 8 9380 2734
School of Physics, M013                         Fax: +61 8 9380 1014
The University of Western Australia      (CRICOS Provider No 00126G)
35 Stirling Highway
Crawley WA 6009                      mailto:paul at physics.uwa.edu.au
AUSTRALIA                            http://physics.uwa.edu.au/~paul

```

• Prev by Date: Re: Symbolic matrix manipulation
• Next by Date: RE: Font size
• Previous by thread: RE: Creating a symmetric matrix
• Next by thread: Re: Creating a symmetric matrix