morphmet
Mon, 02 Jun 2008 08:02:29 -0700
-------- Original Message -------- Subject: RE: variance in shape Date: Mon, 2 Jun 2008 07:14:03 -0700 (PDT) From: F. James Rohlf <[EMAIL PROTECTED]> Reply-To: [EMAIL PROTECTED] Organization: Stony Brook University To: morphmet@morphometrics.org References: <[EMAIL PROTECTED]>Doing that does not really measure the amount of variance. It is a measure of variance among relative to variance within the a priori defined groups.
It would be better to first perform a GPA of all specimens at once so as to project them all into a common tangent space. You can then use standard methods to compare variation in the two groups (e.g., compare determinants, trace, or largest root of their covariance matrices).
------------------------ F. James Rohlf, Distinguished Professor Ecology & Evolution, Stony Brook University www: http://life.bio.sunysb.edu/ee/rohlf
-----Original Message----- From: morphmet [EMAIL PROTECTED] Sent: Monday, June 02, 2008 8:59 AM To: morphmet Subject: variance in shape -------- Original Message -------- Subject: variance in shape Date: Sun, 1 Jun 2008 16:41:20 -0700 (PDT) From: Chris Harrod <[EMAIL PROTECTED]> To: morphmet@morphometrics.org <morphmet@morphometrics.org> Dear all out there in morpholand. I want to examine variance in shape between fish found in allopatry and those found in sympatry with a putative competitor. Can I simply compare the variance in DF/CVA scores (based on the normal landmark analyses) between different populations, or am I being horribly simplistic? thanks in advance Chris ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> Dr Chris Harrod Lecturer in Fish and Aquatic Ecology Ecology and Evolutionary Biology Queen's University Belfast School of Biological Sciences Medical Biology Centre 97 Lisburn Road Belfast BT9 7BL UK [EMAIL PROTECTED] Tel: +44 (0) 28 90972271 Mob: +44 (0) 79 77419314 Fax: +44 (0) 28 90975877 http://www.qub.ac.uk/schools/SchoolofBiologicalSciences/Staff/DrCHarrod / <>< <>< <>< <>< <>< <>< <>< <>< <>< <>< <>< <>< <>< <>< -- Replies will be sent to the list. For more information visit http://www.morphometrics.org
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