R help - Oct 2005 - Writing point pattern to a file

Hi,

	I am trying to use the R package 'spatstat' for generating spatial 
poisson point process graphs. I can create a point pattern using the 
following commands:

	pp <- rpoispp(.01, win=owin(c(0,100),c(0,100)))

	and also view the resulting graph by:

	plot(pp)

	But how can I export the generated point pattern to an external file so 
that I could use it as input for some network simulation
programs ? Also, it seems that the generated graph is different on each 
invocation. Is there a way I could control this randomness, some seed 
perhaps.

Thanks in advance,
Ajit.
-- 
Ajit Chakrapani Warrier
------------------------------------------------------------
Graduate Student                     acwarrie at csc.ncsu.edu
Department of Computer Science       (919) 389 9737
North Carolina State University      www4.ncsu.edu/~acwarrie

Ajit Chakrapani Warrier wrote:
> 	pp <- rpoispp(.01, win=owin(c(0,100),c(0,100)))
> 	But how can I export the generated point pattern to an external file so 
> that I could use it as input for some network simulation
> programs ? 
  You can get the coordinates of a point-pattern object with the $x and 
$y components. You can write to a file with R's 'write.table'
function.
So make the $x and $y components into a matrix, and use write.table. 
Here I'll use some write.table options to make a fairly clean file, 
coordinates separated by commas, with no row names, and nothing stuck in 
quote marks:

write.table(file="ppxy.csv",cbind(pp$x,pp$y),sep=",",row.names=FALSE,col.names=c('x','y'),quote=FALSE)

 > Also, it seems that the generated graph is different on each
 > invocation. Is there a way I could control this randomness, some seed
 > perhaps.

See the help for 'set.seed' - type 'help(set.seed)'

Baz