----- Forwarded message from Carmelo Fruciano -----
Date: Wed, 20 Jun 2012 12:51:25 -0400
From: Carmelo Fruciano
Reply-To: Carmelo Fruciano
Subject: Re: Size correction for shape analysis
To: morphmet@morphometrics.org
morphmet_modera...@morphometrics.org ha scritto:
>
> ----- Forwarded message from kalpana das -----
>
> Date: Fri, 15 Jun 2012 03:34:29 -0400
> From: kalpana das
> Reply-To: kalpana das
> Subject: Size correction for shape analysis
> To: morphmet@morphometrics.org
>
> Dear all,
> I have a little confusion here regarding the need of correcting size
> for shape analysis.
> As far as I understand size factor tend to be removed during
> Procrustes superimposing.
Yes, but allometric variation in shape is still there...
> But to remove the size factor it Should know the size in the first
> place,so If my images are not calibrated that means its lacking
> information on size.In this case how the superimposition method
> remove the size factor.
> Is it appropriate to use uncalibrated images for analysis?
The superimposition (I imagine you're talking about Generalized
Procustes Analysis) uses the coordinates that it gets and scales them
to unit centroid size. If, for wathever reason, you're not interested
in a correct computation of centroid size (i.e. you're only interested
in analysing shape), I guess it's fine to use "uncalibrated images" (I
imagine you're referring to the "Scale" option of the TPS files).
I hope this helps...
Carmelo
--
Carmelo Fruciano
Post-doc - University of Konstanz - Konstanz, Germany
Honorary Fellow - University of Catania - Catania, Italy
e-mail c.fruci...@unict.it
http://www.fruciano.it/research/
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