From: Michael <comtech.usa_at_gmail.com>

Date: Wed 24 May 2006 - 16:14:21 EST

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed May 24 16:19:49 2006

Date: Wed 24 May 2006 - 16:14:21 EST

imagine when you have complicated matrix algebra computation using R,

you cannot prevent some middle-terms become quadratic and absorbs into one scalar, right?

if R cannot intelligently determine this, and you have to manually add "drop" everywhere,

do you think it is reasonable?

On 5/23/06, Patrick Burns <pburns@pburns.seanet.com> wrote:

*>
**> I think
**>
**> drop(B/D) * solve(A)
**>
**> would be a more transparent approach.
**>
**> It isn't that R can not do what you want, it is that
**> it is saving you from shooting yourself in the foot
**> in your attempt. What you are doing is not really
**> a matrix computation.
**>
**>
**> Patrick Burns
*

> patrick@burns-stat.com

*> +44 (0)20 8525 0696
**> http://www.burns-stat.com
**> (home of S Poetry and "A Guide for the Unwilling S User")
**>
**> Michael wrote:
**>
**> >This is very strange:
**> >
**> >I want compute the following in R:
**> >
**> >g = B/D * solve(A)
**> >
**> >where B and D are quadratics so they are just a scalar number, e.g.
**> B=t(a)
**> >%*% F %*% a;
**> >
**> >I want to multiply B/D to A^(-1),
**> >
**> >but R just does not allow me to do that and it keeps complaining that
**> >"nonconformable array, etc."
**> >
**> >
**> >I tried the following two tricks and they worked:
**> >
**> >as.numeric(B/D) * solve(A)
**> >
**> >diag(as.numeric(B/D), 5, 5) %*% solve (A)
**> >
**> >----------------------------
**> >
**> >But if R cannot intelligently do scalar and matrix multiplication, it is
**> >really problemetic.
**> >
**> >It basically cannot be used to do computations, since in complicated
**> matrix
**> >algebras, you have to distinguish where is scalar, and scalars obtained
**> from
**> >quadratics cannot be directly used to multiply another matrix, etc. It is
**> >going to a huge mess...
**> >
**> >Any thoughts?
**> >
**> > [[alternative HTML version deleted]]
**> >
**> >______________________________________________
**> >R-help@stat.math.ethz.ch mailing list
**> >https://stat.ethz.ch/mailman/listinfo/r-help
**> >PLEASE do read the posting guide!
**> http://www.R-project.org/posting-guide.html
**> >
**> >
**> >
**> >
**>
*

[[alternative HTML version deleted]]

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed May 24 16:19:49 2006

Archive maintained by Robert King, hosted by
the discipline of
statistics at the
University of Newcastle,
Australia.

Archive generated by hypermail 2.1.8, at Tue 30 May 2006 - 02:10:24 EST.

*
Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-help.
Please read the posting
guide before posting to the list.
*