[R-sig-Geo] Clip a shpae file with a grid

[Robert J. Hijmans]

Dear Puneet,

To clip a grid with a your polygon 'vector' you can do:

library(raster)
r = raster( extent(-117026, 582149, 2783590, 3443337) )
res(r) = 10000
rc = crop(r, vector)

If you want to know which cells are land and which are not:
rp = polygonsToRaster(vector, rc, field=-1)
plot(rp)

# rp is now a RasterLayer object with cell values 1 where the polygons
overlaps the center of the cell and NA in other cells.

plot(rp)

Robert


On Fri, Apr 9, 2010 at 8:00 AM, Dwivedi,Puneet <puneetd at ufl.edu> wrote:
> Dear All,
>
> I have created a grid for the State of FL using following command:
>
> locpred = expand.grid(X=seq(-117026, 582149, 10000), Y=seq(2783590, 3443337, 10000))
> plot(locpred)
>
> The Gulf of Mexico is also included in the above grid.
>
> I am using following command to import a shape file of FL:
>
> library(maptools)
> vector = readShapePoly("County_BND.shp")
> plot(vector)
>
> Now, I am looking for some code which can help me in obtaining exact grid of FL using above imported shape file as a clipping surface.
>
> It will be great if somebody can guide me on the same as I am not getting any success in finding the code. Alternate procedure is also welcome!
>
> Cheers,
> Puneet Dwivedi
>
>
>        [[alternative HTML version deleted]]
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at stat.math.ethz.ch
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>