[Rd] ?eigen documentation suggestion

From: Dan Davison <davison_at_stats.ox.ac.uk>
Date: Thu, 29 Nov 2007 11:34:18 +0000


from ?eigen

symmetric: if 'TRUE', the matrix is assumed to be symmetric (or

          Hermitian if complex) and only its lower triangle is used. If
          'symmetric' is not specified, the matrix is inspected for
          symmetry.


I think that could mislead a naive reader as it suggests that, with symmetric=TRUE, the result of eigen() (vectors and values) depends only on the lower-triangular values, and thus not on the values on the diagonal (that's not true for the eigenvalues).

I suggest that changing it to

"... and only its lower triangle is used when computing the eigenvectors."

would be more accurate, perhaps even with a reminder about the trace - sum of eigenvalues relationship.

Dan



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