Re: creating a symbolic square symmetric matrix

*To*: mathgroup at smc.vnet.net*Subject*: [mg66334] Re: creating a symbolic square symmetric matrix*From*: "Ray Koopman" <koopman at sfu.ca>*Date*: Wed, 10 May 2006 06:33:20 -0400 (EDT)*References*: <e3pege$ifq$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

> Hi, > First, I created a square matrix with the following command : > n=4; > mat=Table[Subscript[a,i, j],{i,n},{j,n}] > In the same style, I would like to create a symmetric matric where all > a[i, j] is replaced by a[j,i] for i>j. For i<=j, the coefficients > remain in place. > I tried to use the replace command : > Replace[mat,Subscript[a,i,j]->Subscript[a,j,i]] > This just interchanged the elements. I want this replacement only for > the lower or upper triangular matrix elements. > Would appreciate tips of doing a conditional substitution. > /ravi Table[ Subscript[a, Sequence@@Sort@{i,j}], {i,n},{j,n}] will do it.