Thanks Robert, much appreciated.


On Tue, Jan 7, 2014 at 1:57 PM, Robert J. Hijmans <r.hijmans@gmail.com>wrote:

> Tim,
>
> To count the number of points (obsdeep) in each polygon, you can do:
>
> table( over(SpatialPoints(obsdeep), poly) )
>
> There is no role for rasterizing polygons here. But to answer your
> question: you are getting a count of 1 because there is never more
> than 1 polygon that matches a raster cell (no overlapping polygons).
>
> Robert
>
>
>
> On Tue, Jan 7, 2014 at 12:25 PM, Tim Sippel <tsippel@gmail.com> wrote:
> > Hi-
> > I need to count the number of observations in each of 8 polygons.  I'm
> > using the raster package for this, but am having trouble getting what I
> > need. Why am I getting a count of 1 in each of the polygons defined
> below?
> >
> > Sample data can be downloaded here:
> >
> https://drive.google.com/file/d/0B0d3zfSSPFQsVS04aExhbl9hUU0/edit?usp=sharing
> >
> >
> > library(raster)
> >
> > #polygons
> > reg1<-Polygon(coords=cbind(c(200,220,220,200,200), c(0,0,10,10,0)));
> > r1<-Polygons(list(reg1), 'reg1')
> > reg2<-Polygon(coords=cbind(c(185,200,200,185,185), c(0,0,10,10,0)));
> > r2<-Polygons(list(reg2), 'reg2')
> > reg3<-Polygon(coords=cbind(c(200,225,225,200,200), c(10,10,20,20,10)));
> > r3<-Polygons(list(reg3), 'reg3')
> > reg4<-Polygon(coords=cbind(c(180,200,200,180,180), c(10,10,20,20,10)));
> > r4<-Polygons(list(reg4), 'reg4')
> > reg5<-Polygon(coords=cbind(c(200,225,225,200,200), c(20,20,30,30,20)));
> > r5<-Polygons(list(reg5), 'reg5')
> > reg6<-Polygon(coords=cbind(c(180,200,200,180,180), c(20,20,30,30,20)));
> > r6<-Polygons(list(reg6), 'reg6')
> > reg7<-Polygon(coords=cbind(c(200,235,235,200,200), c(30,30,45,45,30)));
> > r7<-Polygons(list(reg7), 'reg7')
> > reg8<-Polygon(coords=cbind(c(180,200,200,180,180), c(30,30,45,45,30)));
> > r8<-Polygons(list(reg8), 'reg8')
> > poly<-SpatialPolygons(Srl=list(r1,r2,r3,r4,r5,r6,r7,r8), pO=1:8)
> >
> > #raster setup
> > xmn=170; xmx=240; ymn=-5; ymx=50
> > grid<-raster(nrows=length(seq(ymn,ymx,by=5))-1,
> > ncols=length(seq(xmn,xmx,by=5))-1, xmn=xmn, xmx=xmx, ymn=ymn, ymx=ymx);
> grid
> >
> > # rasterize & plot
> > obsdeep<-rasterize(x=poly, y=grid, field=obs.deep$Longitude1,
> fun="count")
> > plot(obsdeep); plot(poly, add=T)
> >
> > Many thanks,
> >
> > Tim
> >
> >         [[alternative HTML version deleted]]
> >
> > _______________________________________________
> > R-sig-Geo mailing list
> > R-sig-Geo@r-project.org
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>

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