Re: creating a symbolic square symmetric matrix

*To*: mathgroup at smc.vnet.net*Subject*: [mg66336] Re: creating a symbolic square symmetric matrix*From*: Heinz Spindler <heinz at mathematik.Uni-Osnabrueck.DE>*Date*: Wed, 10 May 2006 06:33:26 -0400 (EDT)*Organization*: Universitaet Hannover*References*: <e3pege$ifq$1@smc.vnet.net>*Reply-to*: Heinz.Spindler at mathematik.Uni-Osnabrueck.DE*Sender*: owner-wri-mathgroup at wolfram.com

ravi wrote: >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 > > hi, use the condition " /;i>j " in the definition of your symmetric matrix Subscript[a,i_,j_]/;i>j:=Subscript[a,j,i] mat[n_]:=Table[Subscript[a,i,j],{i,n},{j,n}] example: mat[3]//MatrixForm Heinz Spindler