----- Forwarded message from Carmelo Fruciano <[email protected]> -----
Date: Tue, 26 Feb 2013 03:52:26 -0500
From: Carmelo Fruciano <[email protected]>
Reply-To: Carmelo Fruciano <[email protected]>
Subject: Re: TPS outlining method
To: [email protected]
[email protected] ha scritto:
>
> ----- Forwarded message from Eloise Cave -----
>
> Date: Sat, 23 Feb 2013 15:19:34 -0500
> From: Eloise Cave
> Reply-To: [email protected]
> Subject: TPS outlining method
> To: [email protected]
>
> Greetings,
> I am currently trying to do some geometric analysis on stingray
> teeth. I would only like to determine a difference in one section of
> the teeth. I am using TPS to outline the teeth however I just need
> some tips. If I want to just determine a difference on part of a
> tooth instead of the entire thing, can I outline just that section
> or should I still outline the entire tooth?
Dear Eloise,
I would say that if your interest is one section, I would try to focus
on that section...wether or not you can clearly and consistently
define that section is, of course, another story...I guess you'll
probably have this problem...
> Also, how many landmarks/semilandmarks should I have on the outline?
> I know that there has to be a point that is the same in all
> specimens but how many points is good enough?
I don't think there is a "right" answer for this second question. I
guess it both depends on the problem at hand and on the biological
shape you want to capture. In certain situations (for instance, when
you already know that two groups are different and just want to find
the best number of (semi)landmarks to maximize the difference between
two groups) you might find some sort of logical criterion to choose
(Procrustes distance between means VS number of points). In most
cases, however, the criterion to choose the "best" number of
(semi)landmarks is not so easy to define and then, in my opinion, you
are left with your own best judgement.
Best,
Carmelo
--
Carmelo Fruciano
Post-doc - University of Konstanz - Konstanz, Germany
Honorary Fellow - University of Catania - Catania, Italy
e-mail [email protected]
http://www.fruciano.it/research/
----- End forwarded message -----
