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Re: creating a symbolic square symmetric matrix


> 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.


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