[R-sig-Geo] circular window for spatial statistics (spatstat package)

[Roger Bivand]

For completeness, see the correct way of making circular windows in the
off-thread:

http://article.gmane.org/gmane.comp.lang.r.geo/1351
https://stat.ethz.ch/pipermail/r-sig-geo/2007-March/001865.html

reply by Adrian Baddeley, using disc() in the spatstat package.


On Tue, 13 Mar 2007, Roger Bivand wrote:

> On Tue, 13 Mar 2007, Michael Friendly wrote:
> 
> > Hi list,
> > 
> > A biology student I'm trying to help has done a study planting 20 seeds 
> > in circular pots under varying conditions and wants to analyze the 
> > degree of clustering
> > (and other measures) in the seeds that germinate (0-20) in relation to
> > the factors that differentiate pots (treatment, type of seed, ...)
> > 
> > The data structure is something like a data frame for all the 
> > germinating seeds, recording (X,Y) location and maybe some other
> > measure like size after xx days:
> > 
> > PotID Treatment SeedType  X    Y  size
> > 
> > Assume that the (X,Y) locations are referred to a circle of fixed radius, R.
> > I'm not very familiar with analysis of spatial point processes, but it 
> > seems that the spatstat package could handle this.  (Is there something
> > better?)  I've read the documentation, but can't find an example of how 
> > to specify a circular window for the ppp object that would contain the
> > data and the window.
> 
> Maybe March is a circular month? There was a thread on this recently:
> 
> http://article.gmane.org/gmane.comp.lang.r.geo/1320
> 
> refering to John Fox's original:
> 
> http://finzi.psych.upenn.edu/R/Rhelp02a/archive/74907.html
> 
> For a single pot, you'd need an owin object in the coordinate system of 
> the X,Y, best if the pot centre and radius were recorded. Then the 
> locations of the germinated seeds in each pot would become a ppp object 
> with a known owin (generated as a circumference sequence). Should the 
> clustering measure be at the seed observation or the pot plot level?
> 
> Hope this helps,
> 
> Roger 
> 
> > 
> > thanks,
> > -Michael
> > 
> > 
> 
> 

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no