Hi all,
I've got the following matrix :
?
mat <- matrix(rnorm(700), ncol=5, dimnames=list( paste("f", c(1:140), sep="_"), c("A", "B", "C", "D", "E")))
I can see that currently most of the multivariate Hotelling T2 tests are limited for application on two groups/samples.
I wud appreciate if someone can provide me a suggestion how to implement the same for multiple groups.
Thx,
- Vickie
Hotelling T2 test extension for multigroup data
3 messages · Vickie S, Peter Dalgaard
On Feb 9, 2012, at 12:11 , Vickie S wrote:
Hi all,
I've got the following matrix :
mat <- matrix(rnorm(700), ncol=5, dimnames=list( paste("f", c(1:140), sep="_"), c("A", "B", "C", "D", "E")))
I can see that currently most of the multivariate Hotelling T2 tests are limited for application on two groups/samples.
I wud appreciate if someone can provide me a suggestion how to implement the same for multiple groups.
Please don't start up a new thread, cloning the same misconceptions as an earlier one! It doesn't help, you will only get people misunderstanding you in the same way... Apparently, you have rows and columns reversed relative to the common layout in multivariate analysis. Also, you have only one observation for each of your "groups" (species)? What makes you think that T^2 would work for you if you had only "A" and "B" species? I don't think anything will work unless you have either replication or some sort of additional assumptions on the covariance structure of your 140-dimensional response.
Peter Dalgaard, Professor Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com
Hey Peter, I agree that Hotelling's T test, although technically possible for two groups but rejecting the Ho in this case is not going to convey any meaning. But I am sure there is a possibility. My assumption is based on using simulated reference set for each comparison. -- Vickie ----------------------------------------
Subject: Re: [R] Hotelling T2 test extension for multigroup data
From: pdalgd at gmail.com
Date: Thu, 9 Feb 2012 14:08:22 +0100
CC: r-help at r-project.org
To: isvik at live.com
On Feb 9, 2012, at 12:11 , Vickie S wrote:
Hi all,
I've got the following matrix :
mat <- matrix(rnorm(700), ncol=5, dimnames=list( paste("f", c(1:140), sep="_"), c("A", "B", "C", "D", "E")))
I can see that currently most of the multivariate Hotelling T2 tests are limited for application on two groups/samples.
I wud appreciate if someone can provide me a suggestion how to implement the same for multiple groups.
Please don't start up a new thread, cloning the same misconceptions as an earlier one! It doesn't help, you will only get people misunderstanding you in the same way...
Apparently, you have rows and columns reversed relative to the common layout in multivariate analysis. Also, you have only one observation for each of your "groups" (species)?
What makes you think that T^2 would work for you if you had only "A" and "B" species? I don't think anything will work unless you have either replication or some sort of additional assumptions on the covariance structure of your 140-dimensional response.
--
Peter Dalgaard, Professor
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com