raster (version 1.9-5)

Arith-methods: Arithmic with Raster* objects

Description

Standard arithmic operators for computations with Raster* objects and numeric values. The following operators are available: +, -, *, /, ^, %%, %/% Input Raster* objects should have the same extent, origin and resolution. If only the extent differs, the computation will continue for the intersection of the Raster objects. Operators are applied on a cell by cell basis. For a RasterLayer, numeric values are recycled by row. For a RasterStack or RasterBrick, recycling is done by layer. RasterLayer objects can be combined RasterStack/Brick objects, in which case the RasterLayer is 'recycled'. When using multiple RasterStack or RasterBrick objects, the number of layers of these objects needs to be the same.

Value

• A Raster* object, and in some cases the side effect of a new file on disk.

Details

If the values of the output Raster* cannot be held in memory, they will be saved to a temporary file. You can use options to set the default file format, datatype and progress bar.

See Also

Math-methods, overlay, calc

Examples

r1 <- raster(ncols=10, nrows=10)
r1[] <- runif(ncell(r1))
r2 <- setValues(r1, 1:ncell(r1) / ncell(r1) )
r3 <- r1 + r2
r2 <- r1 / 10
r3 <- r1 * (r2 - 1 + r1^2 / r2)

# recycling by row
r4 <- r1 * 0 + 1:ncol(r1)

# multi-layer object mutiplication, no recycling
b1 <- brick(r1, r2, r3)
b2 <- b1 * 10

# recycling by layer
b3 <- b1 + c(1, 5, 10)

# adding twoh RasterBrick objects
b3 <- b2 + b1

# summing two RasterBricks and one RasterLayer. The RasterLayer is 'recycled'
b3 <- b1 + b2 + r1