----- Forwarded message from "F. James Rohlf" <[email protected]> -----
Date: Sun, 27 Oct 2013 08:37:18 -0400
From: "F. James Rohlf" <[email protected]>
Reply-To: [email protected]
Subject: RE: combining linear and geometric measurements
To: [email protected]
The problem with performing a PCA on such a mixture of data types is that PCA
is not invariant to the units of measurement used. Linear measurements are not
in the same units as the usual shape variables for shapes in Kendall's shape
space or tangent space. DFA and CVA do not have that problem as their results
are scale invariant. However, they have the problem of needing larger sample
sizes than is often practical.
----------------------
F. James Rohlf, John S. Toll Professor, Stony Brook University
The much revised 4th editions of Biometry and Statistical Tables are now
available:
http://www.whfreeman.com/Catalog/product/biometry-fourthedition-sokal
http://www.whfreeman.com/Catalog/product/statisticaltables-fourthedition-rohlf
Please consider the environment before printing this email
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]
> Sent: Sunday, October 27, 2013 4:39 AM
> To: [email protected]
> Subject: combining linear and geometric measurements
>
>
> ----- Forwarded message from Bryan Stephen McLean <[email protected]> -----
>
> Date: Fri, 25 Oct 2013 17:35:52 -0400
> From: Bryan Stephen McLean <[email protected]>
> Reply-To: Bryan Stephen McLean <[email protected]>
> Subject: combining linear and geometric measurements
> To: "[email protected]" <[email protected]>
>
> Hi everyone,
>
> An issue that I’m sure someone can provide insight on…
>
> I have a mix of traditional (linear) measurements and geometric morphometric
> (2D landmark) data from several rodent taxa that I would like to perform
> PCA/DFA on to hopefully discriminate groups based on ecomorpholoy.
>
> What is the best way to combine these 2 types of data?? Can they simply be
> appended and PCA performed as usual??
>
> Thanks much-
> -Bryan
>
> Bryan McLean
> Department of Biology and
> Museum of Southwestern Biology
> MSC03-2020
> University of New Mexico
> Albuquerque, NM 87131
>
> ----- End forwarded message -----
----- End forwarded message -----
