Hi Nicolas, Sender: [EMAIL PROTECTED] Precedence: bulk I did not see this review you mention, but I reproduce hereunder the definitions given to "form" and "shape" in the glossary of Slice et al.
form - In morphometrics, we represent the form of an object by a point in a space of form variables, which are measurements of a geometric object that are unchanged by translations and rotations. If you allow for reflections, forms stand for all the figures that have all the same interlandmark distances. A form is usually represented by one of its figures at some specified location and in some specified orientation. When represented in this way, location and orientation are said to have been "removed." shape variable - Any measure of the geometry of a biological form, or the image of a form, that does not change under similarity transformations: translations, rotations, and changes of geometric scale (enlargements or reductions). Useful shape variables include angles, ratios of distances, and any of the sets of shape coordinates that arise in geometric morphometrics. So that, according to me, "form" could be assimilated to the "object" itself; shape is this object from which size has been removed. The many ways "size" can be removed produce different shape matrices, but with the same property: variables independent of the kind of size which has been (tentatively) removed ... Sometimes these variables contain allometric residuals, or they contain isometric residuals, or both: it depends on the procedure of size removal. Jean-Pierre Dujardin -----Original Message----- From: Nicol�s Jaramillo O. [mailto:[EMAIL PROTECTED] Sent: Saturday, March 29, 2003 11:55 AM To: [EMAIL PROTECTED] Cc: Harling Caro- Ria�o; Dr. Jean Pierre Dujardin Subject: shape vs form Dear Morphometricians, I have difficulty defining the concepts "form" and "shape". Following the review posted at the SUNY Stony Brook webpage by Adams, Rohlf and Slice, matrices containing average distances between pairs of landmarks for each sample being compared are form matrices because they include both size and shape information. On the other hand, if one subtracts the means from a matrix of log-transformed variables (i.g. if one subtracts the isometric component), could be named the residual matrix a form matrix because it have both size and shape information (allometry)? In multivariate analyses as CPCA or mgPCA, size effects could be sequestered in one variable (first PC) rendering matrices free of allometric effects as can be verified indirectly by linear regression. In this case, how I could name those matrices? It is not easy for me to understand the concept of shape free of allometry. Is it defined only for need (or convenience) in the multivariate statistics, or actually can it be found in biological structures? Please excuse me my poorly defined grammatical structure of English. Thanks in advance, Nicol�s Nicol�s Jaramillo O. M.S., Ph.D. Professor, Instituto de Biolog�a, Universidad de Antioquia A.A. 1226, Medell�n, Colombia Phone: (+57 4) 210 5626, Fax: (+57 4) 233 01 20 E-mail: [EMAIL PROTECTED]; [EMAIL PROTECTED] == Replies will be sent to list. For more information see http://life.bio.sunysb.edu/morph/morphmet.html.
