Displaying 20 results from an estimated 600 matches similar to: "GLM Repeated measures test of assumptions: e.g. test for sphericity e.g. Bartletts and Levenes homogenous variances"
2009 Dec 01
0
Amendment to previous post a minute ago, please amend before posting if possible
Sorry, I just posted the email below but realised I did not give a name or
details, would it be possible to adjust before posting and send what is
below, sorry again, first time user...
From: Joanne Lenehan [mailto:jlenehan@une.edu.au]
Sent: Tuesday, 1 December 2009 3:51 PM
To: 'r-help@r-project.org'
Subject: GLM Repeated measures test of assumptions: e.g. test for sphericity
e.g.
2010 Jan 11
0
tweedie.profile error message
Good afternoon
My name is Joanne Lenehan, I am a post grad at UNE using R version 2.9.0
I came across the Tweedie package in old R help posts and was interested in
giving it a go for some data.
The data is below and also attached as BaregroundLitterLogs
Site
Treatment
Graze
Dam
Plot
Time
Bare
Litter
Logs
1
C
remote
yes
1
A
0
2
0
1
C
remote
yes
2
A
0
15
0
1
HE
2013 Oct 29
0
Mean error
Hi,
Try either:
res1 <- apply(mydata[,1:2],2,mean)
?res2 <- colMeans(mydata[,1:2])
?identical(res1,res2)
#[1] TRUE
# Also if you need to find means for each group ("Ungrazed vs. "Grazed")
by(mydata[,-3],mydata[,3],colMeans)
#or if column names are "V1", "V2", "V3"
aggregate(.~V3,mydata,mean)
#or
library(plyr)
2010 Jan 19
1
restricted permutations in permtest()?
Hallo List,
I'm trying to implemement a restricted permutation scheme in permutest(). More
precisely I have dependence in my data that should be allowed for in the
permutation - I simulated the problem in the example of the vegan documentation
p.24:
library(vegan)
data(varespec)
## Bray-Curtis distances between samples
dis <- vegdist(varespec)
## First 16 sites grazed, remaining 8 sites
2003 Dec 05
0
simple sphericity test using bartlett and cov?
Hey,
Is this right for a sphericity test?
x <- mymatrix
mycov <- cov(x)
bartlett.text (array (mycov), myconditions)
2011 Jun 17
4
Bartlett's Test of Sphericity
Hello Dear R user,
I want to conduct a Principal components analysis and I need to run two
tests to check whether I can do it or not. I found how to run the KMO
test, however i cannot find an R fonction for the Bartlett's test of
sphericity. Does somebody know if it exists?
Thanks for your help!
Thibault
[[alternative HTML version deleted]]
2011 Jun 18
1
"Justify" PCA? -- was: Bartlett's Test of Sphericity
Apologies for the obvious, but just to clarify: there is no reason to
"justify" a PCA -- it's just an eigen decomposition of a matrix and is
therefore "justified" by linear algebra.
If one wants to determine whether some subset of the eigenvectors =
principal components suffice to "represent" the data in some sense,
then that is where distributional
2008 Aug 07
2
panel.arrows problem in custom panel function
Dear List,
I am writing a custom panel function and xyplot method to plot the
results of a procrustes analysis from the vegan package.
I am having trouble getting the call to panel.arrows to work as I wish
when conditioning. The attached file contains the function definitions
for the xyplot method and the custom panel and prepanel functions I am
using. This example, using data and functions from
2006 Mar 24
0
Random covariate in survreg (Survival)
Dear R Listers-
I am attempting to analyse the survival of seeds in cages
(exclosures) that differ in their permeability to rainforest mammals.
Because I did not observe the moment of seed disappearance, my data
is interval censored. This limits my options for analysis (as I
understand it) to survreg, in the survival package. Because I
repeated the experiment in 8 sites, I have a random
2009 May 27
1
Hierarchical glm with binomial family
Dear members of the R help list,
I want to do a hierarchical glm with binomial family but am unsure
about how to write the syntax which involves nesting.
I want to test whether the risk of being attacked by Herbivores for
Meadowsweet plants is significantly dependent on the Distance to
heterospecific source plants.
Dependent variable = Herbivory (yes/no)
Explanatory continuous variable =
2003 Dec 13
0
sphericity calculation (more formulas?)
I believe that the following function is a good function for eyeballing
sphericity. But, I can't find functions for tests anywhere (g-g or
h-f). Anyone who wants to can feel free to use it.
It is bad that R does not provide any tests for sphericity AND cannot
do a MANOVA on repeated measures (although lme is an alternative add on
package). One of these solutions must be provided in the
2006 Mar 20
1
does lme repeated measures require sphericity?
I haven't been able to find an answer on this that's direct, only
implied. In several places I have read that when people asked for
sphericity tests they were guided toward lme or mlm models. But,
there is no direct indication that the lme method is not subject to
the sphericity assumption. In fact, it seems like it should be. Its
just a linear model that handles random and
2007 Aug 21
2
Sphericity test in R for repeated measures ANOVA
Hi,
Is there a way to do a sphericity test in R for repeated measures ANOVA
(using aov or lme)? I can't find anything about it in the help.
Thanks
Orou
[[alternative HTML version deleted]]
2004 Jun 23
1
Sphericity test
Hi R-users
Does anybody know if there are functions or packages in R for sphericity
tests like Bartlett's or Mauchly's?
Thanks!
__________________________________________________________
Eng. Agr., M.Sc. Eduardo Dutra de Armas
__________________________________________________________
Centro de Energia Nuclear na Agricultura (CENA/USP)
Laboratório de Ecotoxicologia
Av.Centenário 303,
2005 May 10
1
sphericity calculation
Dear Prof. Baron,
thankyou for your pdf paper on using R, at
http://www.psych.upenn.edu/~baron/rpsych.pdf
I am currently interested in the sphericity notes on pp. 45-47.
The equation on p. 46 suggests the following R calculation:
D <- k^2 * ( mean(diag(S)) - mean(S) )^2
while the notes in the pdf indicate the following:
D <- k^2 * ( mean(S) - mean(diag(S)) )^2
Can you please consider
2011 Mar 10
1
power for repeated-measures ANOVA lacking sphericity
Is there a function that calculates the power of a
repeated-measure ANOVA design, e.g., 2 groups, 4
within-subject factors, an average 0.40 correlation between
the 4 within factors, etc.
I don't think I can use power.anova.test() because it does
not consider corr=0.40.
I am hoping that someone has already implemented the method
by Muller & Barton (1989, JASA 84: 549-555) on how to
2000 Aug 24
0
Is there a method to calculate Huynh and Feldt adjustments for sphericity violations
Hi,
I'm getting to grips with using R to perform repeat measures
analysis of variance and was wondering is there a potted method to
obtain Huynh and Feldt or other adjustments for sphericity
violations?
Thanks
Dominic
Dr Dominic J Barraclough
Dept Neurobiology and Anatomy,
University of Rochester,
601 Elmwood Av, Box 603,
Rochester
NY 14642
tel (716) 2753627
dominic_barraclough at
2007 Mar 26
0
Sphericity and post-hoc analysis in a repeated-measure ANOVA
Does anyone have any suggestions for how to test for violation of the
sphericity assumption and apply the Huynh-Feldt correction to a
repeated-measure model? My model follows the format below:
Rep.anova=aov(Y~X1*X2+Error(Subject/(X1*X2),data=DataFile))
I've already looked at the explanations aov() and Error() in Baron's
“Notes on the use of R for psychology experiments and
2009 Nov 09
1
Getting Sphericity Tests for Within Subject Repeated Measure Anova (using "car" package)
Hello everyone,
I am trying to do within subjects repeated measures anova followed by the
test of sphericity (sample dataset below).
I am able to get either mixed model or linear model anova and TukeyHSD, but
have no luck with Repeated-Measures Assuming Sphericity or Separate
Sphericity Tests.
I am trying to follow example from "car" package, but it seems that I am not
getting something
2009 Mar 03
1
repeated measures anova, sphericity, epsilon, etc
I have 3 questions (below).
Background: I am teaching an introductory statistics course in which we are
covering (among other things) repeated measures anova. This time around
teaching it, we are using R for all of our computations. We are starting by
covering the univariate approach to repeated measures anova.
Doing a basic repeated measures anova (univariate approach) using aov()
seems