Just remember that if you have measurement error in the X variable then you likely underestimate the true slope:
Ives, A. R., P. E. Midford, and T. Garland. 2007. Within-species variation and measurement error in phylogenetic comparative methods. Systematic Biology 56:252–270. Also, if you have soft polytomies then you may want to subtract some d.f.: Purvis, A., and T. Garland, Jr. 1993. Polytomies in comparative analyses of continuous characters. Systematic Biology 42:569–575. Cheers, Ted Theodore Garland, Jr., Professor Department of Biology University of California, Riverside Riverside, CA 92521 Office Phone: (951) 827-3524 Facsimile: (951) 827-4286 (not confidential) Email: tgarl...@ucr.edu http://www.biology.ucr.edu/people/faculty/Garland.html http://scholar.google.com/citations?hl=en&user=iSSbrhwAAAAJ Director, UCR Institute for the Development of Educational Applications Editor in Chief, Physiological and Biochemical Zoology Fail Lab: Episode One http://testtube.com/faillab/zoochosis-episode-one-evolution http://www.youtube.com/watch?v=c0msBWyTzU0 ________________________________________ From: r-sig-phylo-boun...@r-project.org [r-sig-phylo-boun...@r-project.org] on behalf of Xavier Prudent [prudentxav...@gmail.com] Sent: Thursday, August 21, 2014 3:06 AM To: Gustavo Paterno Cc: r-sig-phylo@r-project.org Subject: Re: [R-sig-phylo] How to test if the slope is different from 1 in PGLS? Hi Gustavo, GLS returns the estimated slope and its uncertainty, you can then compute a t-value where your null-hypothesis is "slope=1", and from that t-value get a p-value. Cheers, Xavier 2014-08-20 21:30 GMT+02:00 Gustavo Paterno <paterno...@gmail.com>: > Dear all, > I am working with flower allometry and want to use PGLS to analyse how the > male and female biomass of the flower scale with total flower biomass. > So simple linear regressions, but log-trasformed. > > my model is: > mod.male <- pgls(male~total, data=flower.data,lambda="ML") > > Besides calculating the slope of the regression I am also interested to > test if the slope is different then 1. How can I do this in PGLS? > I would be very glad if any one could help me with that. > > Kind regards, > Gustavo Paterno > ----------------------------------------- > Gustavo B. Paterno > Doutorando em Ecologia > Departamento de Ecologia > Universidade Federal do Rio Grande do Norte > Natal, Brasil > ------------------------------------- > skype: gustavopaterno > pater...@cb.ufrn.br > > > > > > > > > > > > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-phylo mailing list - R-sig-phylo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-phylo > Searchable archive at > http://www.mail-archive.com/r-sig-phylo@r-project.org/ > -- *---------------------------------------Xavier Prudent* *Computational biology and evolutionary genomics* *Guest scientist at the Max-Planck-Institut für Physik komplexer Systeme* *(MPI-PKS)* *Noethnitzer Str. 38* *01187 Dresden * *Max Planck-Institute for Molecular Cell Biology and Genetics* *(MPI-CBG)* *Pfotenhauerstraße 108 * *01307 Dresden* *Phone: +49 351 210-2621* *Mail: prudent [ at ] mpi-cbg.de <http://mpi-cbg.de>* *---------------------------------------* [[alternative HTML version deleted]] _______________________________________________ R-sig-phylo mailing list - R-sig-phylo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-phylo Searchable archive at http://www.mail-archive.com/r-sig-phylo@r-project.org/ _______________________________________________ R-sig-phylo mailing list - R-sig-phylo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-phylo Searchable archive at http://www.mail-archive.com/r-sig-phylo@r-project.org/
