That is indeed happening in my sample but also this 'bunching-up' appears in taxa where the structure's (in this case the beak) relative size is much bigger than in average specimens, should this be happening? I tried the latest version of tpsRelw as well and recover the same pattern.
Cheers, 2016-08-24 18:32 GMT+01:00 F. James Rohlf <[email protected]>: > An advantage of the bending energy approach is that it minimizes the > chance of collapsing landmarks because changes in the positions of > landmarks that are close together requires much more bending energy. This > is not usually a problem but it can be if the outline has a sharp corner - > which seems likely for a beak. > > ---------------------- > F. James Rohlf New email: [email protected] > Distinguished Professor, Emeritus. Dept. of Ecol. & Evol. > & Research Professor. Dept. of Anthropology > Stony Brook University 11794-4364 > 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: Guillermo Navalón [mailto:[email protected]] > Sent: Monday, August 22, 2016 9:34 AM > To: MORPHMET <[email protected]> > Subject: [MORPHMET] Problems with min-dsquare sliding in tpsRelw > > Hi everyone, > > In a very disparate sample of bird skulls I am using a configuration with > both lnmdks and smlndmks. Specifically, to capture the lateral morphology > of the beak (likely the most variable area) I digitized 2 curves with 15 > evenly-spaced semilandmarks. > > The 2 curves are constrained by 3 regular lndmks forming a triangle, the > tip-of-the-beak landmark (landmark 1) is the anterior end of both curves. > > When I slide the smlndmks in tpsRelw with min-dsquare slide method some of > the anterior smlndmks collapse in a very narrow section in both of the 2 > curves in the Procrustes superimposition. This effect is not affecting to > the other curve in the configuration (midline of the neurocranium) that is > apparently much less variable in my sample. Also, minimum bending energy > slide method does not affect the superimposition in this way, but I want to > try to use min-dsquare. > > I have tried to change the slide maximum iterations and slide recursive > options but still recover the same effect. > > > Any idea what is going on here? Is it a bug of the program or is it a > proper statistical effect? > > Thank you! > > Guillermo Navalón > > -- > MORPHMET may be accessed via its webpage at http://www.morphometrics.org > --- > You received this message because you are subscribed to the Google Groups > "MORPHMET" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > > -- MORPHMET may be accessed via its webpage at http://www.morphometrics.org --- You received this message because you are subscribed to the Google Groups "MORPHMET" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
