On Mon, 20 Feb 2006, Alain Paquette wrote: > Hello R people > > I now know how to run my discriminant analysis with the lda function in > MASS: > lda.alain=lda(Groupes ~ Ht.D0 + Lc.Dc + Ram + IDF, gr, CV = FALSE) > and it works fine.
CV=FALSE is the default and so not needed. > But I am missing a test and cannot find any help on how to get it, if it > exist. > > The "S" equivalent: There is no such function in S, and I rather object as the S equivalent is lda() (and as the author of both I should know). Credit where credit is due: discrim() is an S-PLUS function, indebted to lda(). > discrim(structure(.Data = Groupes ~ Ht.D0 + Lc.Dc + Ram + IDF, class = > "formula"), data = gr, family = Canonical(cov.structure = > "homoscedastic"), na.action = na.omit, prior = "proportional") > outputs a nice matrix of Mahalanobis distances between groups and even > tests (Hotelling's T Squared) for significant distances. Well, it seems not to. That is part of the output of the summary() method, which itself calls the multicomp() method. > Why don't I just take the "S" output you say? Because like you, I'd > rather put in my paper that I did it using R of course! No `of course' applies. If you learnt of this output from S-PLUS, I urge you to credit it honestly and accurately. (If you refer to lda, you should credit that, not just R.) > Does anyone know of a way to get this test out of lda? Or of another R > package that does it? Mahalanobis distance between groups is easy, as this is just Euclidean distance between group centres in the scaled space. The test statistics can be produced, but - they are critically dependent on the unrealistic assumptions of multivariate normality and variance homogeneity and - there needs to be an adjustment for multiple comparisons. -- Brian D. Ripley, [EMAIL PROTECTED] 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 ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
