[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


   should be an element-wise product because it is so in R.

   What if M is a matrix?  It is useful to have


   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


   should be the usual number obtained by  u * (M *n)


           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
Phone/FAX 250-655-3364

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