[R] Coding matrix equation

Joshua Wiley
Mon, 11 Apr 2011 08:11:27 -0000

Hi Matt,

Petr gave you one possibility.  If you are looking for more matrix
operations see:

?"%*%" # the inner product of the matrices
?"%o%" # the outer product of the matrices
?"(" # for parentheses to help order things

require(MASS) # load the package MASS

?ginv # for the generalized inverse of a matrix

For things like constants which you just want treated normally, use
the regular multiplication operator, "*", not the matrix one.

HTH,

Josh

On Mon, Apr 11, 2011 at 12:43 AM, matthew.r.robinson at sheffield.ac.uk
<matthew.r.robinson at sheffield.ac.uk> wrote:
> Hi all,
>
> I have two matrices:
>
> G<-matrix(c(2.0, 0.5, 0.5, 0.5, 2.0, 0.5, 0.5, 0.5,2.0),3,3)
> P<-matrix(c(1.0, 0.5, 0.5, 0.5, 1.0, 0.5, 0.5, 0.5,1.0),3,3)
>
> and I want to run this equation to get a new matrix F:
>
> F = [P+2G]^-1/2 P [P+2G]^-1/2
>
> Could someone please tell me how to code this in R?
>
> Many thanks in advance for your time.
>
> Best wishes,
> Matt
>
> ? ? ? ?[[alternative HTML version deleted]]
>
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--
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles