Re: [MORPHMET] model II regression statistics PAST

2016-03-12 Thread Mauro Cavalcanti 
Patrick,

PAST is "free" as in "free beer", not as in *free speech*. It is gratis,
but not open. The problem you have is just typical of such black box
approach to scientific software development -- since one cannot see the
source code, it is not possible to check how this or that algorithm is
implemented.

Stick to R, where nothing is hidden.

Best regards,

2016-03-12 11:49 GMT-03:00 Patrick Arnold :

> Dear morphometrics,
>
> I am frequently using PAST (paleontological statistics; what a great free
> software) for the analysis of morphometric data (geometric and
> traditional). Now I want to do a reduced major axis regression on bivariate
> data (only one Y for each X). However, I do not found the possibility to
> perform a significance test for the regression (F statistics) or for the
> slope and intercept (t statistics).
> It is provided for least square regression (e.g., under polynomial option)
> but not for model II regression. Does anyone know a possibility to obtain
> regression statistics in PAST for model II regressions?
> Thanks in advance.
>
> Cheers
> Patrick
>
>
> --
> Patrick Arnold, M.Sc.
>
> wissenschaftlicher Mitarbeiter und Doktorand
> Institut für Spezielle Zoologie und Evolutionsbiologie
> mit Phyletischem Museum
> Friedrich-Schiller-Universität Jena
> Erbertstraße 1
> 07743 Jena
> Germany
>
> Phone:  +49 (0)3641 9-49165
> Fax:+49 (0)3641 9-49142
> E-mail: patrick.arn...@uni-jena.de
>
> --
> MORPHMET may be accessed via its webpage at http://www.morphometrics.org
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>
>


-- 
Dr. Mauro J. Cavalcanti
E-mail: mauro...@gmail.com
Web: http://sites.google.com/site/maurobio

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[MORPHMET] Using photographs from distinct sources to GM analyses

2016-03-12 Thread Pablo Fisichella 
Dear Morphometricians

I am new in geometric morphometrics. I have a question perhaps quite simple
with regards to 2D GM. I am comparing the size/shape of human skulls from
different sources using photographs taken in norma lateralis. One part was
obtained through a standardized protocol while the other part was obtained
from published pictures (with permissions) which were obtained using
different protocols. I have traditional measurements for each skull for the
published data set in order to compute the centroid size. However, taking
into account some theoretical issues I feel that such comparison may be
biased especially regarding size (i.e. CS) because both sets of images were
obtained using different distances between the camera and the target. In
order to minimize the size bias I plan to digitize landmarks and
semilandmarks only along the skull contour given that its shape can be
optimally characterized using a 2D approach. The location of landmarks in
other structures poorly characterized from the 2D approach (i.e distinct to
the contour) would increase the size bias. I will do a procrustes analysis
using both data sets and through a multivariate regression of size on the
procustes coordinates I will obtain residuals (i.e. shape variables). To my
knowledge using this approach I will minimize the size bias mentioned.
Obviously I will not use the centroid size in any subsequent analysis, only
the shape variables. Does anyone tell me if this approach is right? Some
suggestions?
thanks in advance

cheers
Pablo


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Re: [MORPHMET] model II regression statistics PAST

2016-03-12 Thread N. MacLeod 
I can’t help you with PAST, but this reference will allow you to compute the 
correct statistics for a standardized major axis (often erroneously called a 
reduced major axis) regression.

Warton, D. I., et al., 2006, Bivariate line-fitting methods for allometry: 
Biological Reviews, v. 81, no. 2, p. 259–291.

Norm MacLeod



> On 12 Mar 2016, at 14:49, Patrick Arnold  wrote:
> 
> Dear morphometrics,
> 
> I am frequently using PAST (paleontological statistics; what a great free 
> software) for the analysis of morphometric data (geometric and traditional). 
> Now I want to do a reduced major axis regression on bivariate data (only one 
> Y for each X). However, I do not found the possibility to perform a 
> significance test for the regression (F statistics) or for the slope and 
> intercept (t statistics).
> It is provided for least square regression (e.g., under polynomial option) 
> but not for model II regression. Does anyone know a possibility to obtain 
> regression statistics in PAST for model II regressions?
> Thanks in advance.
> 
> Cheers
> Patrick
> 
> 
> -- 
> Patrick Arnold, M.Sc.
> 
> wissenschaftlicher Mitarbeiter und Doktorand
> Institut für Spezielle Zoologie und Evolutionsbiologie
> mit Phyletischem Museum
> Friedrich-Schiller-Universität Jena
> Erbertstraße 1
> 07743 Jena
> Germany
> 
> Phone:  +49 (0)3641 9-49165
> Fax:+49 (0)3641 9-49142
> E-mail: patrick.arn...@uni-jena.de
> 
> -- 
> MORPHMET may be accessed via its webpage at http://www.morphometrics.org
> ---You received this message because you are subscribed to the Google Groups 
> "MORPHMET" group.
> To unsubscribe from this group and stop receiving emails from it, send an 
> email to morphmet+unsubscr...@morphometrics.org.
> 

_

Professor Norman MacLeod
Dean of Postgraduate Education and Training
The Natural History Museum, Cromwell Road, London, SW7 5BD
(0)207 942-5204 (Office Landline)
(0)785 017-1787 (Mobile)
http://www.nhm.ac.uk/hosted_sites/paleonet/MacLeod/

Department of Earth Sciences, University College
London, Gower Street, London WC1E 6BT, UK

Nanjing Institute of Geology & Palaeontology,
Chinese Academy of Sciences, 39 Beijing, Donglu, Nanjing, China
_








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