crop: Cut out a geographic subset

In terra: Spatial Data Analysis

Cut out a geographic subset

Description

Cut out a part of a SpatRaster or SpatVector.

You can crop a SpatRaster with a SpatExtent, or with another object from which an extent can be obtained. Note that the SpatRaster returned may not have the exactly the same extent as the SpatExtent supplied because you can only select entire cells (rows and columns), and you cannot add new areas. See methods like resample and disagg to force SpatRasters to align and extend to add rows and/or columns.

You can only crop rectangular areas of a SpatRaster, but see argument mask=TRUE for setting cell values within SpatRaster to NA; or use the mask method after crop for additional masking options.

You can crop a SpatVector with another SpatVector. If these are not polygons, the minimum convex hull is used. Unlike with intersect the geometries and attributes of y are not transferred to the output. You can also crop a SpatVector with a rectangle (SpatRaster, SpatExtent).

Usage

## S4 method for signature 'SpatRaster'
crop(x, y, snap="near", mask=FALSE, touches=TRUE, extend=FALSE, filename="", ...)

## S4 method for signature 'SpatRasterDataset'
crop(x, y, snap="near", extend=FALSE)

## S4 method for signature 'SpatRasterCollection'
crop(x, y, snap="near", extend=FALSE)

## S4 method for signature 'SpatVector'
crop(x, y, ext=FALSE)

## S4 method for signature 'SpatGraticule'
crop(x, y)

Arguments

x	SpatRaster or SpatVector
y	SpatRaster, SpatVector, SpatExtent, or any other object that has a SpatExtent (ext returns a SpatExtent)
snap	character. One of "near", "in", or "out". Used to align y to the geometry of x
mask	logical. Should y be used to mask? Only used if y is a SpatVector, SpatRaster or sf
touches	logical. If TRUE and mask=TRUE, all cells touched by lines or polygons will be masked, not just those on the line render path, or whose center point is within the polygon
extend	logical. Should rows and/or columns be added if y is beyond the extent of x? Also see extend
filename	character. Output filename
...	additional arguments for writing files as in writeRaster
ext	logical. Use the extent of y instead of y. This also changes the behavior when y is an extent in two ways: (1) points that are on the extent boundary are removed and (2) lon/lat extents that go beyond -180 or 180 degrees longitude are wrapped around the earth to include areas at the other end of the dateline

Value

SpatRaster

See Also

intersect, extend

See window for a virtual and sometimes more efficient way to crop a dataset.

Examples

r <- rast(xmin=0, xmax=10, ymin=0, ymax=10, nrows=25, ncols=25)
values(r) <- 1:ncell(r)
e <- ext(-5, 5, -5, 5)
rc <- crop(r, e)

# crop and mask
f <- system.file("ex/elev.tif", package="terra")
r <- rast(f)
f <- system.file("ex/lux.shp", package="terra")
v <- vect(f)
cm <- crop(r, v[9:12,], mask=TRUE)
plot(cm)
lines(v)

# crop vector
f <- system.file("ex/lux.shp", package="terra")
v <- vect(f)
e <- ext(6.15, 6.3, 49.7, 49.8)
x <- crop(v, e)
plot(x, "NAME_1")

terra documentation built on Oct. 14, 2024, 5:07 p.m.