raster: area – R documentation

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area

Size of cells

Description

Raster objects: Compute the approximate surface area of cells in an unprojected (longitude/latitude) Raster object. It is an approximation because area is computed as the height (latitudinal span) of a cell (which is constant among all cells) times the width (longitudinal span) in the (latitudinal) middle of a cell. The width is smaller at the poleward side than at the equator-ward side of a cell. This variation is greatest near the poles and the values are thus not very precise for very high latitudes.

SpatialPolygons: Compute the area of the spatial features. Works for both planar and angular (lon/lat) coordinate reference systems

Usage

## S4 method for signature 'RasterLayer'
area(x, filename="", na.rm=FALSE, weights=FALSE, ...)

## S4 method for signature 'RasterStackBrick'
area(x, filename="", na.rm=FALSE, weights=FALSE, ...)

## S4 method for signature 'SpatialPolygons'
area(x, ...)

Arguments

`x`	Raster* or SpatialPolygons object
`filename`	character. Filename for the output Raster object (optional)
`na.rm`	logical. If `TRUE`, cells that are `NA` are ignored
`weights`	logical. If `TRUE`, the area of each cells is divided by the total area of all cells that are not `NA`
`...`	additional arguments as for `writeRaster`

Details

If x is a RasterStack/Brick, a RasterBrick will be returned if na.rm=TRUE. However, if na.rm=FALSE, a RasterLayer is returned, because the values would be the same for all layers.

Value

If x is a Raster* object: RasterLayer or RasterBrick. Cell values represent the size of the cell in km2, or the relative size if weights=TRUE

If x is a SpatialPolygons* object: area if each spatial object in squared meters if the CRS is longitude/latitude, or in squared map units (typically meter)

Examples

r <- raster(nrow=18, ncol=36)
a <- area(r)

if (require(rgdal) & require(rgeos)) {
	p <- shapefile(system.file("external/lux.shp", package="raster"))
	p$area <- round(area(p) / 10000000,1)
	p$area
}

raster

Geographic Data Analysis and Modeling

v3.4-10

GPL (>= 3)

Authors

Robert J. Hijmans [cre, aut] (<https://orcid.org/0000-0001-5872-2872>), Jacob van Etten [ctb], Michael Sumner [ctb], Joe Cheng [ctb], Dan Baston [ctb], Andrew Bevan [ctb], Roger Bivand [ctb], Lorenzo Busetto [ctb], Mort Canty [ctb], Ben Fasoli [ctb], David Forrest [ctb], Aniruddha Ghosh [ctb], Duncan Golicher [ctb], Josh Gray [ctb], Jonathan A. Greenberg [ctb], Paul Hiemstra [ctb], Kassel Hingee [ctb], Institute for Mathematics Applied Geosciences [cph], Charles Karney [ctb], Matteo Mattiuzzi [ctb], Steven Mosher [ctb], Babak Naimi [ctb], Jakub Nowosad [ctb], Edzer Pebesma [ctb], Oscar Perpinan Lamigueiro [ctb], Etienne B. Racine [ctb], Barry Rowlingson [ctb], Ashton Shortridge [ctb], Bill Venables [ctb], Rafael Wueest [ctb]

Initial release

2021-05-02