[ADMB Users] operators in ADMB or R got it wrong
dave fournier
otter at otter-rsch.com
Wed Aug 12 09:36:35 PDT 2009
It is often said that if u and v are vectors in ADMB then
u*v
should be an element-wise product because it is so in R.
What if M is a matrix? It is useful to have
M*v
be the product of a matrix times a vector yielding another vector.
If M and N are both matrices then M*N should be matrix
multiplication. If M represents a quadratic form then
u*M*v
should be the usual number obtained by u * (M *n)
and
u*M*inv(M)*v should be equal to u * Id *v = u*v
All of this speaks to the fact that u*v should be the dot product and
R got it wrong.
--
David A. Fournier
P.O. Box 2040,
Sidney, B.C. V8l 3S3
Canada
Phone/FAX 250-655-3364
http://otter-rsch.com
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