crop: Crop

Description

crop returns a geographic subset of an object as specified by an Extent object (or object from which an extent object can be extracted/created). If x is a Raster* object, the Extent is aligned to x. Areas included in y but outside the extent of x are ignored (see extend if you want a larger area).

Usage

# S4 method for Raster
crop(x, y, filename="", snap='near', datatype=NULL, ...)
# S4 method for Spatial
crop(x, y, ...)

Value

RasterLayer or RasterBrick object; or SpatialLines or SpatialPolygons object.

Arguments

x: Raster* object or SpatialPolygons*, SpatialLines*, or SpatialPoints* object
y: Extent object, or any object from which an Extent object can be extracted (see Details)
filename: Character, output filename. Optional
snap: Character. One of 'near', 'in', or 'out', for use with alignExtent
datatype: Character. Output dataType (by default it is the same as the input datatype)
...: Additional arguments as for writeRaster

Details

Objects from which an Extent can be extracted/created include RasterLayer, RasterStack, RasterBrick and objects of the Spatial* classes from the sp package. You can check this with the extent function. New Extent objects can also be created with function extent and drawExtent by clicking twice on a plot.

To crop by row and column numbers you can create an extent like this (for Raster x, row 5 to 10, column 7 to 12) crop(x, extent(x, 5, 10, 7, 12))

Examples

Run this code

r <- raster(nrow=45, ncol=90)
values(r) <- 1:ncell(r)
e <- extent(-160, 10, 30, 60)
rc <- crop(r, e)	

# use row and column numbers:
rc2 <- crop(r, extent(r, 5, 10, 7, 15))

# crop Raster* with Spatial* object
b <- as(extent(6, 6.4, 49.75, 50), 'SpatialPolygons')
crs(b) <- crs(r)
rb <- crop(r, b)

# crop a SpatialPolygon* object with another one
p <- shapefile(system.file("external/lux.shp", package="raster"))
pb <- crop(p, b)