----- Forwarded message from Dean Adams
<dcad...@iastate.edu> -----
Date: Fri, 26 Apr 2013 10:20:35
-0400
From: Dean Adams <dcad...@iastate.edu>
Reply-To:
Dean Adams <dcad...@iastate.edu>
Subject: Re: 2B-PLS vs PLSR
To: morphmet@morphometrics.org
Rodrigo,
The two methods are identical; plsr() is just an implementation of two-block partial least squares. To obtain the PLS correlation between primary PLS vectors in plsr(), do:
pls.res<- plsr(Y ~ X)
cor(pls.res$scores[,1],pls.res$Yscores[,1])
The same result could also be found 'by hand' following the steps in Rohlf and Corti 2000: obtain the cross-covariance matrix S.XY, decompose it via SVD, project the data onto the vectors, and find their correlation.
Dean
The two methods are identical; plsr() is just an implementation of two-block partial least squares. To obtain the PLS correlation between primary PLS vectors in plsr(), do:
pls.res<- plsr(Y ~ X)
cor(pls.res$scores[,1],pls.res$Yscores[,1])
The same result could also be found 'by hand' following the steps in Rohlf and Corti 2000: obtain the cross-covariance matrix S.XY, decompose it via SVD, project the data onto the vectors, and find their correlation.
Dean
-- Dr. Dean C. Adams Professor Department of Ecology, Evolution, and Organismal Biology Department of Statistics Iowa State University Ames, Iowa 50011 www.public.iastate.edu/~dcadams/ phone: 515-294-3834
On 4/25/2013 4:45 PM,
morphmet_modera...@morphometrics.org wrote:
----- Forwarded message from Rodrigo Lima <rodrigo.l...@mail.mcgill.ca> -----
Date: Wed, 24 Apr 2013 09:57:46 -0400
From: Rodrigo Lima <rodrigo.l...@mail.mcgill.ca>
Reply-To: Rodrigo Lima <rodrigo.l...@mail.mcgill.ca>
Subject: 2B-PLS vs PLSR
To: "morphmet@morphometrics.org" <morphmet@morphometrics.org>Dear morphometricians,
I have a question about the PLS analysis and I would be very thankful for any insight provided.
What is the difference between two-block PLS (as in Rohf and Corti 2000) and PLS regression (PLSR) implemented in the pls package in R (Mevik and Wehrens 2007)? I'm trying to relate skull shape to climatic variables, which one would be more appropriate in this case?
Thank you,
Rodrigo
----- End forwarded message -----
----- End forwarded message
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