Thank you Roger,
I thought i needed to extract the polygon to assign it to the pip function.
overlay also worked for me in terms of assigning polygon IDs to the points.
Perhaps a little extra work, but it got me to where i needed to be!

On Sat, Mar 19, 2011 at 4:02 PM, Roger Bivand <Roger.Bivand@nhh.no> wrote:

> On Wed, 16 Mar 2011, david depew wrote:
>
>  Dear list, I'd like to loop through all polygons in a shapefile, and count
>> the # of points of interest in each polygon. I see previous postings
>> suggest
>> a for loop should work, but I'm not able to extract the individual
>> polygons.
>> I post the following portion since I can get to this point in my
>> script....but the extraction step fails (most likely due to my inability
>> to
>> specify what part of the SpatialPolygonsDataFrame to extract.....
>>
>> library(sp)
>> library(maptools)
>> library(splancs)
>> library(rgdal)
>> library(spdep)
>> nc.sids <- readShapePoly(system.file("etc/shapes/sids.shp",
>> package="spdep")[1],
>>  ID="FIPSNO", proj4string=CRS("+proj=longlat +ellps=clrk66"))
>> rn <- sapply(slot(nc.sids, "polygons"), function(x) slot(x, "ID"))
>>
>> for (i in 1:length(rn)) {
>> temp.poly= ---- effectively, rn[i], i.e. a polygon with ID=="i". I can
>> then
>> assign data from the result of the pip function, but I'm having difficulty
>> extracting each polygon sequentially to do this.
>>
>
> Why do you need to extract the polygons?
>
> pts <- spsample(nc.sids, n=5000, type="random")
> plot(nc.sids, axes=TRUE)
> points(pts, pch=".")
> out <- over(xx, pts)
>
> where out is a vector with a count for each Polygons object in nc.sids. You
> will have more work to do if you need to count in each Polygon object within
> each Polygons object, but that would imply that the input data need
> reorganising.
>
> Hope this helps,
>
> Roger
>
>
>
>> Any help is much appreciated!
>>
>> Thanks!
>>
>>
>>
> --
> 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@nhh.no
>
>


-- 
David Depew
Postdoctoral Fellow
School of Environmental Studies
Queen's University
Kingston, Ontario
K7L 3N6

david.depew@queensu.ca
P: (613) 533-6000 x77831

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