-------- Original Message --------
Subject: Re: Regression of Shape with size
Date: Wed, 2 May 2012 10:09:13 -0400
From: Antigoni Kaliontzopoulou <ant...@gmail.com>
To: morphmet@morphometrics.org
Hello Kaplana,
if your images were not made from the same distance and you don't have a
size reference within them that you can use to calibrate and calculate a
scale factor, you are actually lacking information about size in your
coordinates. This means that centroid size is not a "correct" measure of
size in your case (it is OK for the Procrustes superimposition but it
doesn't represent the relative size of your specimens, because it is not
standardised).
You could use SVL as the size measure, but that would give you a result
that is difficult to interpret, as it would tell you about the allometry
of the shape of the structure you are studying on total body size (but
not of shape on size of the structure, which can be tricky because you
can have different allometry components in your system).
The best solution would be if you have some size measure you can use to
calibrate your photographs. This does not need to be necessarily
millimetric paper or a ruler: if you have in your pictures a structure
that you have measured (a linear biometric variable you can see well and
without distortion in the photos), you can use that (you would need to
set the reference lengths for each specimen in tpsDig, say by indicating
the distance between the eyes of each animal and inputting the
equivalent measure).
Hope this helps
Antigoni
On Wed, May 2, 2012 at 8:38 AM, <morphmet_modera...@morphometrics.org
<mailto:morphmet_modera...@morphometrics.org>> wrote:
----- Forwarded message from kalpana das __ -----
Date: Wed, 2 May 2012 06:13:10 -0400
From: kalpana das __
Reply-To: kalpana das __
Subject: Regression of Shape with size
To: morphmet@morphometrics.org <mailto:morphmet@morphometrics.org>
Dear all,
I want to regress the size on shape and want to see how shape is
changing with respect to size.
But i have images without scale factor.
So ,I was just wondering if it is appropriate to use SVL (snout to
vent length in frogs which is equivalent to total body length)
as size instead of centroid size in Tpsregr Programm.
Or is there any other way i can put the scale in images .?
Any kind of suggestion is welcome.
Thank you
Regards,
Kalpana
--
*Kalpana*
MSc.Biodiversity and Conservation(2009-11)
University School of Environment Management
Guru Gobind Sigh Indraprastha University
Dwarka,Delhi-110075
Email- kkalpanaa1...@gmail.com
<http://mailto:email-kkalpanaa1...@gmail.com>
Mobile no-9620313751/8010255368
/"Not everything that counts can be counted, and not everything that
can be counted counts."
/
----- End forwarded message -----
______
--
Antigoni Kaliontzopoulou
CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos
Campus Agrário de Vairão, 4485-661 Vairão
PORTUGAL
Department of Ecology, Evolution, and Organismal Biology
Iowa State University, Ames,
Iowa 50011, USA
tel: +351 91 3086188
mail to: ant...@gmail.com <mailto:ant...@gmail.com>
antig...@mail.icav.up.pt <mailto:antig...@mail.icav.up.pt>
