[R-sig-Geo] [circular window for spatstat]

Michael Friendly friendly at yorku.ca
Thu Mar 15 13:14:24 CET 2007

Thanks very much, Adrian.


Adrian Baddeley wrote:

> On Tue, 13 Mar 2007, Michael Friendly wrote:
>>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.
> To create a circular window in spatstat, you can use the 
> function disc(). See help(disc). 
> For example suppose a point pattern with coordinates x, y (two vectors)
> is observed inside a pot with centre (x0, y0) and radius R.
> Then 
> 	   pot <- disc(R, c(x0,y0))
> creates a window (owin object) representing the pot,
> and
> 	   X <- ppp(x, y, window=pot)
> creates the point pattern. 
> Since spatstat always plots spatial objects isometrically, you can also 
> use plot(disc(....)) just to draw a circle. 
>>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
> Currently, a point pattern can only have one mark variable
> (e.g. you can attach the SeedType to each point, or attach the size to
> each point, but not both).
> This will change in spatstat version 2 which will be released soon.
>>(Is there something better?) 
> There is nothing better than spatstat!  %^]
> regards
> Adrian Baddeley

Michael Friendly     Email: friendly AT yorku DOT ca
Professor, Psychology Dept.
York University      Voice: 416 736-5115 x66249 Fax: 416 736-5814
4700 Keele Street    http://www.math.yorku.ca/SCS/friendly.html
Toronto, ONT  M3J 1P3 CANADA

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