[R] Reconstructing LD function

[Prof Brian Ripley]

On Mon, 27 Jun 2005 usenet at s-boehringer.de wrote:

> in an LDA analysis with n groups n-1 LD functions result. Implicitly this
> defines an LD fucntion for the last group. Does there exist code already
> to explictly construct this LD function?

What `LDA analysis' are our discussing here?  (LDA is usually
`linear discriminant analysis', so what did you mean and what R function 
are you nor referring to?)

R has lda in package MASS, and that works with n LD functions.  To reduce 
it to n-1, subtract the last one from the others, in which case LD_n == 0.

Anything you do in LD analysis only depends on differences in LD
functions, and there really are n of them.  With two groups one is
conventionally taken to be zero (the first, usually, not the last).

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595