-------- Original Message -------- Subject: RE: relative warps to distance matrix? Date: Fri, 14 Mar 2008 10:41:10 -0700 (PDT) From: F. James Rohlf <[EMAIL PROTECTED]> Reply-To: <[EMAIL PROTECTED]> Organization: Stony Brook University To: <[email protected]> References: <[EMAIL PROTECTED]>
Correct, there is no need to weight the relative warps - each is already multiplied by the square root of its corresponding eigenvalue. You do need to use a Euclidean distance coefficient based on all of the relative warps. The result will be identical to Euclidean distances based on the 'weight matrix' of partial warp and uniform component scores so the relative warps do not actually need to be computed for this computation. One can also obtain the identical distances from the GPA aligned configurations if they have been projected into the tangent space so the partial warps and uniform component do not need to be computed either if all you want are these distances. The tangent distance described above is an approximation to the Procrustes distance coefficient (they will be equal to or slightly smaller). Which you use will depend on exactly what you plan to do with the distances. However, for most data these two distances are very highly correlated. Both distances (and the correlation between them) can be obtained using the tpsSmall program. I am not sure what your alternative suggestion is for using the variance at each landmark. ========================= F. James Rohlf Distinguished Professor, Stony Brook University http://life.bio.sunysb.edu/ee/rohlf
-----Original Message----- From: morphmet [mailto:[EMAIL PROTECTED] Sent: Friday, March 14, 2008 12:14 PM To: morphmet Subject: relative warps to distance matrix? -------- Original Message -------- Subject: relative warps to distance matrix? Date: Fri, 14 Mar 2008 07:09:44 -0700 (PDT) From: Katja Peijnenburg <[EMAIL PROTECTED]> To: [email protected] References: <[EMAIL PROTECTED]> Dear morphmet, I have collected shape data of gastropod shells using the TPS software package and thus obtained 18 Relative Warp scores per individual. I would like to convert these data into a single distance matrix to use in a program 'Barrier' that draws 'barriers' between populations onto a geographical map. I noticed that the variance of relative warps is correlated with the proportion of variance they explain, so there seems no need to weigh the different relative warp scores. What does the morphmet community think? What would be the best way to convert Relative Warp scores to a distance matrix, and what distance should be used? Or, alternatively, would it be better to use the variance of each landmark, as was suggested to me by a colleague (using Morpheus)? Thank you very much for your opinion on this. Katja Peijnenburg [EMAIL PROTECTED] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Dr. Katja T.C.A. Peijnenburg Marine Biodiversity, Ecology & Evolution (MARBEE) UCD School of Biology & Environmental Science UCD Science Centre West, room 228 University College Dublin Belfield Dublin 4 Republic of Ireland tel. +353.1.716.2013/2262 fax. +353.1.716.1152 http://www.ucd.ie/zoology/marbee/katja_peijnenburg.html email: [EMAIL PROTECTED] -- Replies will be sent to the list. For more information visit http://www.morphometrics.org
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