merge {terra}

R Documentation

Merge SpatRasters, or merge a SpatVector with a data.frame

Description

Merge multiple SpatRasters to create a new SpatRaster object with a larger spatial extent. The SpatRasters must have the same origin and spatial resolution. In areas where the SpatRasters overlap, the values of the SpatRaster that is first in the sequence of arguments (or in the SpatRasterCollection) will be retained (unless first=FALSE.

There is a also a method for merging SpatVector with a data.frame; that is, to join the data.frame to the attribute table of the SpatVector.

Usage

## S4 method for signature 'SpatRaster,SpatRaster'
merge(x, y, ..., first=TRUE, filename="", overwrite=FALSE, wopt=list())

## S4 method for signature 'SpatRasterCollection,missing'
merge(x, first=TRUE, filename="", ...)

## S4 method for signature 'SpatVector,data.frame'
merge(x, y, ...)

Arguments

x	SpatRaster, SpatRasterCollection, or SpatVector
y	missing if x is a SpatRasterCollection. SpatRaster if x is a SpatRaster. data.frame if x is a SpatVector
...	if x is a SpatRaster: additional objects of the same class as x. If x is a SpatRasterCollection: options for writing files as in writeRaster. If x is a SpatVector, the same arguments as in merge
first	logical. If TRUE, in areas where rasters overlap, the first value that is not NA is used. Otherwise the last value that is not NA is used
filename	character. Output filename
overwrite	logical. If TRUE, filename is overwritten
wopt	list with named options for writing files as in writeRaster

Value

SpatRaster or SpatVector

See Also

Combining tiles with vrt may be more efficient than using merge. See mosaic for averaging overlapping regions.

See classify to merge a SpatRaster and a data.frame and union to combine SpatExtent objects.

Examples

x <- rast(xmin=-110, xmax=-80, ymin=40, ymax=70, res=1, vals=1)
y <- rast(xmin=-85, xmax=-55, ymax=60, ymin=30, res=1, vals=2)
z <- rast(xmin=-60, xmax=-30, ymax=50, ymin=20, res=1, vals=3)

m1 <- merge(x, y, z)
m2 <- merge(z, y, x)
m3 <- merge(y, x, z)

# if you have many SpatRasters, it may be convenient
# to make a SpatRasterCollection
rlist <- list(x, y, z)
rsrc <- sprc(rlist)

m <- merge(rsrc)


## SpatVector with data.frame
f <- system.file("ex/lux.shp", package="terra")
p <- vect(f)
dfr <- data.frame(District=p$NAME_1, Canton=p$NAME_2, Value=round(runif(length(p), 100, 1000)))
dfr <- dfr[1:5, ]
pm <- merge(p, dfr, all.x=TRUE, by.x=c('NAME_1', 'NAME_2'), by.y=c('District', 'Canton'))
pm
values(pm)

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