MANOVA with 3D landmark data

[morphmet_moderator]

----- Forwarded message from lia betti -----

Date: Wed, 20 Jun 2012 09:14:57 -0400
From: lia betti
Reply-To: lia betti
Subject: MANOVA with 3D landmark data
To: "morphmet@morphometrics.org"

Dear all,

 

I'm trying to test for sexual dimorphism in shape in different populations, and I would like to do a MANOVA to test for significant effects of sex, of population, and the interaction between the two variables. I am using 3D landmark data, and I realise that the Procrustes coordinates I obtain after Procrustes superimposition are in a non-euclidean space, and therefore unsuitable for normal MANOVA.  I read that I can use relative warps as data to input in my MANOVA, and solve the problem this way, but I would prefer to use either the Procrustes variables, or the PC scores obtained after projecting the Procrustes variables on a euclidean space (because I then proceed to use Procrustes variables to estimate indices of sexual dimorphism).

My questions are:

1) Can I apply a normal MANOVA on the PC scores, given that they are in Euclidean space? I haven't found any paper or book mentioning this method, and I don't understand why.

2) I think I could in principle use Goodall's F test as an alternative to MANOVA on the Procrustes variables, but MorphoJ specifies that the Procrustes ANOVA  run by the program is suitable only for studies of asymmetry or inter-observer error. Again, I am not sure why. In R, the function for this test is again mentioned only in relation to studies of fluctuating asymmetry. Is there a software I can use to run this test to check for significant effects of sex and population?

 

Thanks!

 

Lia

email: liabe...@yahoo.it

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