[R] Reconstructing LD function
Prof Brian Ripley
ripley at stats.ox.ac.uk
Mon Jun 27 13:18:16 CEST 2005
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
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