[GRASS-user] Re: proximity mapping / site clustering

[Dylan Beaudette]

Sure thing. GRASS, R, PostGIS, QGIS, GDAL -- all worth their weight in
gold if you printed the source code.

GRASS newsletter: see vol. 3 , the article by Roger Bivand:
http://grass.itc.it/newsletter/index.php

 and possibly the summary here:
http://casoilresource.lawr.ucdavis.edu/drupal/node/221

with a small no. of sites, the pam() clustering works well, for larger
sample sizes use clara() : both found in the cluster package. note
that pam() is a specialized version of k-means, but generally more
robust. also note that instructing the algorithm to automatically
standardized the input data is usaully a good idea- but see the
references for details.

clustering around set "medoids" with pam() or set "centroids" with
kmeans() is fairly simple, just see the documents associated with
these functions. the CRAN website will be a good start. also, for some
rather generic R examples and documents see the link:
http://casoilresource.lawr.ucdavis.edu/drupal/node/100

regarding the steiner problem: if you have a chance could you post
some sample data, along with your commands so others can give it a
try. I have been meaning to experiment with the v.net.* commands for
sometime now. if you would like i can post it all on our lab's
website, crediting you. or the GRASS wiki might be another option.

I will post the spatial clustering examples to a formatted webpage in
the next couple of days for clarity.

Good luck,

Dylan



On 7/22/06, M S <mseibel at gmail.com> wrote:
>
> ok... given you have a bunch of sites as points say 50 sites.  and you have
> another set of points say 3.
>
> is there a way to cluster the 50 sites to or around the 3 other points?
> sort of using a gravity model to cluster the 50 points to the 3 in the
> shortest distance?
>
>
>
> On 7/22/06, M S <mseibel at gmail.com> wrote:
> >
> >
> > this is awesome.  i cant thank you enough.  i am long time arc/info user
> and know GIS very well.  i've been getting into grass recently, but it is
> takign a large larning curve to untrain my mind from the E$RI way of doing
> things.  you could never do this with arc/info.  like you said the
> flexibility of grass and R make this so sweet!
> >
> > I might have to learn R too.  funny it is from the S package from Bell
> Labs because my dad used to work for them, then ATT then Lucent.  he has
> been working with this stuff a long time and i am just now showing him how
> GRASS GIS can solve the network planning problems.
> >
> > i'll have to look at the article from recent grass newsletter.  i dont
> think i get that publication.  is it off the main website?
> >
> > thanks so much.  this is very encouraging and awesome!
> >
> >
> >
> > On 7/22/06, Dylan Beaudette < dylan.beaudette at gmail.com> wrote:
> > > Indeed. The examples posted were using standard numerical clustering,
> > > which just happened to incorporate spatial coordinates. the packages
> > > mentioned up thread are probably better suited for spatial studies.
> > > Also, see the most recent GRASS Newsletter for a great article by R.
> > > Bivand on getting raster / point data into R.
> > >
> > > Good luck,
> > >
> > > Dylan
> > >
> >
>
>