Merge Raster* objects using a function for overlapping areas

Mosaic Raster* objects to form a new object with a larger spatial extent. A function is used to compute cell values in areas where layers overlap (in contrast to the merge function which uses the values of the 'upper' layer). All objects must have the same origin, resolution, and coordinate reference system.

Usage

# S4 method for class 'Raster,Raster'
mosaic(x, y, ..., fun, tolerance=0.05, filename="")

Arguments

x: Raster* object
y: Raster* object
...: Additional Raster or Extent objects (and/or arguments for writing files as in writeRaster)
fun: Function. E.g. mean, min, or max. Must be a function that accepts a 'na.rm' argument
tolerance: Numeric. permissible difference in origin (relative to the cell resolution). See all.equal
filename: Character. Output filename (optional)

Details

The Raster objects must have the same origin and resolution.

Value

RasterLayer or RasterBrick object.

Examples

r <- raster(ncol=100, nrow=100)
r1 <- crop(r, extent(-10, 11, -10, 11))
r2 <- crop(r, extent(0, 20, 0, 20))
r3 <- crop(r, extent(9, 30, 9, 30))

values(r1) <- 1:ncell(r1)
values(r2) <- 1:ncell(r2)
values(r3) <- 1:ncell(r3)

m1 <- mosaic(r1, r2, r3, fun=mean)

s1 <- stack(r1, r1*2)
s2 <- stack(r2, r2/2)
s3 <- stack(r3, r3*4)
m2 <- mosaic(s1, s2, s3, fun=min)

# if you have a list of Raster objects, you can use do.call
x <- list(r1, r2, r3)
names(x)[1:2] <- c('x', 'y')
x$fun <- mean
x$na.rm <- TRUE

y <- do.call(mosaic, x)