[R-sig-Geo] Clip a raster

[Robert J. Hijmans]

Paulo,

If the polygon does not cover half the edge-pixel, it is ignored. That
should probably change so that all cells that are touched are
included.

To be safe you could use a slightly larger extent, as in:

e <- intersectExtent(x, extent(y))  + 2 * xres(x)

crop(x, e)


Robert

On Fri, Oct 15, 2010 at 8:50 AM, Paulo Brando <paulobrando at gmail.com> wrote:
> Dear All,
>
> I have been using the crop function in the raster package, but haven't
> figured out yet how this function deals with pixels that falls on the edge
> of a polygon.
>
> Thanks,
>
> Paulo
>
> On Thu, Oct 14, 2010 at 12:42 PM, Manuel Spínola <mspinola10 at gmail.com>
> wrote:
>>
>>  Thank you very much Robert.
>> That's works perfect.
>>
>> Manuel
>>
>> On 14/10/2010 10:21 a.m., Robert J. Hijmans wrote:
>> > Manuel,
>> >
>> > if "costarica" is a SpatialPolygons* object, you can do:
>> >
>> > r<- raster("bio1_23.bil")
>> > cr<- crop(r, costarica)
>> >
>> > Robert
>> >
>> > On Thu, Oct 14, 2010 at 8:16 AM, Manuel Spínola<mspinola10 at gmail.com>
>> >  wrote:
>> >>   Dear list members,
>> >>
>> >> I download bioclim data in a raster format (estension: .bil) and I
>> >> would
>> >> like to clip the variables to a ploygon stored as a shapefile (Costa
>> >> Rica outline).
>> >> How can I do that?
>> >>
>> >> I read the raster file like this:
>> >>
>> >> x<- readGDAL("bio1_23.bil")
>> >>
>> >> Thank you very much in advance.
>> >> Best,
>> >>
>> >> Manuel
>> >>
>> >>
>> >> --
>> >> *Manuel Spínola, Ph.D.*
>> >> Instituto Internacional en Conservación y Manejo de Vida Silvestre
>> >> Universidad Nacional
>> >> Apartado 1350-3000
>> >> Heredia
>> >> COSTA RICA
>> >> mspinola at una.ac.cr
>> >> mspinola10 at gmail.com
>> >> Teléfono: (506) 2277-3598
>> >> Fax: (506) 2237-7036
>> >> Personal website: Lobito de río
>> >> <https://sites.google.com/site/lobitoderio/>
>> >> Institutional website: ICOMVIS<http://www.icomvis.una.ac.cr/>
>> >>
>> >>         [[alternative HTML version deleted]]
>> >>
>> >>
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>> >>
>> >>
>>
>>
>> --
>> *Manuel Spínola, Ph.D.*
>> Instituto Internacional en Conservación y Manejo de Vida Silvestre
>> Universidad Nacional
>> Apartado 1350-3000
>> Heredia
>> COSTA RICA
>> mspinola at una.ac.cr
>> mspinola10 at gmail.com
>> Teléfono: (506) 2277-3598
>> Fax: (506) 2237-7036
>> Personal website: Lobito de río
>> <https://sites.google.com/site/lobitoderio/>
>> Institutional website: ICOMVIS <http://www.icomvis.una.ac.cr/>
>>
>>        [[alternative HTML version deleted]]
>>
>>
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>