iological effects of interests are beforehand,
> because we wouldn't know what we measured.
>
> M
>
>
> -Original Message-----
> From: Benedikt Hallgrimsson
> Sent: Thursday, November 8, 2018 11:32 AM
> To: Adams, Dean [EEOBS] ; andrea cardini <
> alcard...@gm
fects of interests are beforehand, bec=
ause we wouldn't know what we measured.
M
-Original Message-
From: Benedikt Hallgrimsson =20
Sent: Thursday, November 8, 2018 11:32 AM
To: Adams, Dean [EEOBS] ; andrea cardini ; morphmet@morphometrics.org
Subject: RE: [MORPHMET] Re: semilandm
logical pragmatism, but I hope some find
this useful.
Benedikt
-Original Message-
From: Adams, Dean [EEOBS]
Sent: Wednesday, November 7, 2018 6:48 AM
To: andrea cardini ; morphmet@morphometrics.org
Subject: RE: [MORPHMET] Re: semilandmarks in biology
Folks,
I think it is importa
of Ecology, Evolution, and Organismal Biology
Iowa State University
www.public.iastate.edu/~dcadams/
phone: 515-294-3834
-Original Message-
From: andrea cardini
Sent: Wednesday, November 7, 2018 4:31 AM
To: morphmet@morphometrics.org
Subject: Re: [MORPHMET] Re: semilandmarks in biology
Making cool pictures has a purpose only if both the pics and the numbers
behind them are accurate. It's not an aim in itself, I hope (although
this is the second time I hear that one should add as many points as
needed to see a nice picture). Parsimonious explanations are, to me,
much more appe
Agreed. In addition, I think it’s important to note that, in the original
implementations of the sliding algorithm, semilandmarks were slid not along the
curve itself, but along tangents to the curve (= off the boundary outline). How
much distortion this induces is, of course, a function of how
Yes, it was always well known that sliding adds covariance but this is
irrelevant for most studies, especially for group mean comparisons and
shape regressions: the kind of studies for which GMM is most efficient, as
Jim noted.
If you consider the change of variance-covariance structure due to
Indeed one of my favourite examples where semilandmarks are really
useful is a paper by Hublin, Gunz et al. (with apologies for the
inaccurate ref. and mixed up order of authors) where they manage to
classify as Neanderthal a piece of cranial vault found (I believe) in
Belgium and possibly in the s
Andrea,
I am intrigued by your initial comment about adding covariance that was
apparently absent. I tend to think of the problem from the other perspective
of not accounting for covariance that should be present. As a thought
experiment (that could probably be simulated, and maybe I am not c
iginal Message-
From: alcardini
Sent: Tuesday, November 6, 2018 12:35 PM
To: F. James Rohlf
Cc: mitte...@univie.ac.at; MORPHMET
Subject: Re: [MORPHMET] Re: semilandmarks in biology
Yes, but doesn't that also add more covariance that wasn't there in the first
place?
Neither l
Yes, but doesn't that also add more covariance that wasn't there in
the first place?
Neither least squares nor minimum bending energy, that we minimize for
sliding, are biological models: they will reduce variance but will do
it in ways that are totally biologically arbitrary.
In the examples I sh
I agree with Philipp but I would like to add that the way I think about the
justification for the sliding of semilandmarks is that if one were smart enough
to know exactly where the most meaningful locations are along some curve then
one should just place the points along the curve and computati
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