Elahep <[email protected]> ha scritto:
Hi morphometricians,
I have a data set consists of 7 landmarks and 7 semi-landmarks on the
carapace of a crab and I want to control my data for the effect of
allometry with tpsRegr. I am not sure which dataset should I use as
dependent variable (presence of semi-landmarks confused me in choosing the
correct dataset as dependent variable!):
1. 1- TPS file consists of landmarks and semi-landmarks *before*
removing the control lines
2. 2- TPS file consists of landmarks and semi-landmarks *after* removing
the control lines
3. 3- TPS file consists of superimposed landmarks and semi-landmarks
(= *Procrustes coordinates*)
Would you please help me with this question?
Dear Elahep,
not sure what you mean with "control lines".
The procedure one generally uses when dealing with semilandmarks is to
perform a generalized Procrustes analysis with sliding of
semilandmarks (typically in tpsRelw), export the aligned coordinates
(and the centroid size, if you want to use that as a measure of body
size) and then treat the exported coordinates as if they were landmarks.
In your case, then, I would imagine you would use in tpsRegr the
aligned coordinates and the centroid size previously exported from
tpsRelw.
Another thing you might want to consider in the process is if your
configuration of landmarks (or, rather, the biological structure
you're trying to capture with them) is symmetric and, if so, if
asymmetry is of interest for you...
Best,
Carmelo
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