Complementing Ted's comment, the randomization test in Blomberg et al. (2003) and the K statistics is available the package "picante". Now, caution is warranted because having many species with the same phenotypic value in the dataset (i.e., many zeros) can dramatically decrease the statistical power of this randomization procedure (see Supplementary information of Rezende et al. 2007 Nature 448: 925 ). Good news is that, if you detect significant signal in your dataset, it is probably there!
All best, Enrico El 25/4/12 12:29 p.m., Theodore Garland Jr escribió: > I would suggest the randomization test in Blomberg et al. (2003). This will > give a valid significance test of the null hypothesis of no phylogenetic > signal. By itself, it does not give a measure of the strength (or amount) of > phylogenetic signal. Not sure if it is implented in r. If not, I can send > our Matlab code. > > Cheers, > Ted > > Theodore Garland, Jr. > Professor > Department of Biology > University of California, Riverside > Riverside, CA 92521 > Office Phone: (951) 827-3524 > Home Phone: (951) 328-0820 > Facsimile: (951) 827-4286 = Dept. office (not confidential) > Email: [email protected] > http://www.biology.ucr.edu/people/faculty/Garland.html > > Experimental Evolution: Concepts, Methods, and Applications of Selection > Experiments. 2009. > Edited by Theodore Garland, Jr. and Michael R. Rose > http://www.ucpress.edu/book.php?isbn=9780520261808 > (PDFs of chapters are available from me or from the individual authors) > > ________________________________________ > From: [email protected] [[email protected]] > on behalf of Nina Hobbhahn [[email protected]] > Sent: Wednesday, April 25, 2012 1:55 AM > To: [email protected] > Subject: [R-sig-phylo] Normality requirement for assessment of lambda with > phylosig (phytools) and fitContinuous (geiger) > > Dear fellow list users, > > I would like to assess the magnitude of phylogenetic signal in two sets of > continuous data. Set 1 contains numerous zeros and is therefore non-normal. > Set 2 contains very little variation and is non-normal due to > underdispersion. Given that both data sets are largely immune to > transformations to normality, I am wondering whether the lambda estimates for > untransformed data derived from phylosig and fitContinuous will be > meaningful? If not, can you recommend transformations or other methods of > phylogenetic-signal assessment that would be preferable? > > Thank you very much, > > Nina > > > > Dr. Nina Hobbhahn > Post-doctoral fellow > Lab of Prof. S. D. Johnson > School of Life Sciences > University of KwaZulu-Natal > Private Bag X01 > Scottsville, Pietermaritzburg, 3201 > South Africa > > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-phylo mailing list > [email protected] > https://stat.ethz.ch/mailman/listinfo/r-sig-phylo > > _______________________________________________ > R-sig-phylo mailing list > [email protected] > https://stat.ethz.ch/mailman/listinfo/r-sig-phylo > -- ************************************************************************ Enrico L. Rezende Departament de Genètica i de Microbiologia Facultat de Biociències, Edifici Cn Universitat Autònoma de Barcelona 08193 Bellaterra (Barcelona) SPAIN Telephone: +34 93 581 4705 Fax: +34 93 581 2387 E-mail: [email protected] ************************************************************************ [[alternative HTML version deleted]]
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