R help - Nov 2011 - calculating symmetric matrix

Hi All,

I need to a calculation W%*%d. However I know that this matrix is symmetric
(since W=t(d)%*%w). My question is considering that I only need to
calculate the lower/ upper triangle (n(n+1)/2 elements) rather than the n^2
elements of the entire matrix. Is there a way to do this efficiently.

My 'n' can be quite large (upto 10,000 or more?).

Thanks,
Sachin

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