[R] least summed square distance + fit

[Peter Ho]

Hi R-users,

Does the function procrustes() do "Generalised Procrustes analysis " (Gower 1975,
Psychometrika, 40,33-51)?

Peter Ho



Bill.Venables at cmis.csiro.au wrote:

> This sounds like procrustes transformations.
>
> There is a function procrustes() in the vegan package to do it.
>
> library(vegan)
> ?procrustes
>
> [Irrelevant side issue: Procrustes was a Greek pirate who used to torture
> his victims by tying them to an iron bed and neatly lopping off any parts of
> their body that protruded.  Not a bad analogy!]
>
> Bill Venables.
>
> -----Original Message-----
> From: Jonathan Baron [mailto:baron at cattell.psych.upenn.edu]
> Sent: Tuesday, May 14, 2002 9:07 PM
> To: Jan Malte Wiener
> Cc: R
> Subject: Re: [R] least summed square distance + fit
>
> Take a look at optim() in the base package.  I've used it for
> things like this, and it works beautifully.  Perhaps there is
> something more specific, but I don't know it.  Jon
>
> On 05/14/02 12:32, Jan Malte Wiener wrote:
> >hi,
> >I have a matrix (representing original data) that looks e.g. like this
> >(consider it beeing x,y,z coords):
> >441     447    0
> >265     407    0
> >374     223    0
> >288     574    0
> >669     309    0
> >591     195    0
> >595     475    0
> >424     351    0
> >
> >I get a second matrix (subject data) that is similiar to the above
> >matrix but it is scaled, translated and rotated (and of course a little
> >inprecise).
> >Also I have an errorfunction that sums up  the squared distances of
> >corresponding points of orig matrix and subject matrix.
> >
> >And here comes my problem:
> >I now need an fitting function that scales, rotates and translates my
> >subject matrix so that the error (computed by the errorfunction) is
> >minimized.
> >Since I am new to R and actually new to that problem, I would be glad if
> >someone could tell me if there is a precompiled fitting procedure that
> >fits my requirements.
> >
> >greetinx jan
> >
> >
> >
> >--
> >Jan Malte Wiener
> >Max-Planck-Institute for Biological Cybernetics
> >Spemannstr. 38, 72076 Tuebingen, Germany
> >Tel.: +49 7071 601 631
> >Email: jan.wiener at tuebingen.mpg.de
> >
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> --
> Jonathan Baron, Professor of Psychology, University of Pennsylvania
> Home page: http://www.sas.upenn.edu/~baron
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