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=enuser=iSSbrhwJ
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
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*---Xavier Prudent*
*Computational biology and evolutionary genomics*
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*(MPI-PKS)*
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*Mail: prudent [ at ] mpi-cbg.de http://mpi-cbg.de*
*---*
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