[R] Efficient testing for +ve definiteness

[Makram Talih]

Dear R-users,

Is there a preferred method for testing whether a real symmetric matrix is
positive definite? [modulo machine rounding errors.]

The obvious way of computing eigenvalues via "E <- eigen(A, symmetric=T,
only.values=T)$values" and returning the result of "!any(E <= 0)" seems
less efficient than going through the LU decomposition invoked in
"determinant.matrix(A)" and checking the sign and (log) modulus of the
determinant.

I suppose this has to do with the underlying C routines. Any thoughts or
anecdotes?

Many Thanks,

Makram Talih

--
Makram Talih, Ph.D.
Assistant Professor
Department of Mathematics and Statistics
Hunter College of the City University of New York
695 Park Avenue, Room 905 HE
New York, NY 10021

Website: http://stat.hunter.cuny.edu/talih
E-mail: makram.talih at hunter.cuny.edu
Tel: 212-772-5308
Fax: 212-772-4858