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Add rows and columns around a writeRaster

Source: R/extend.r
extend.Rd

extend() adds cells around a raster, making it larger.

Usage

# S4 method for class 'GRaster,numeric'
extend(x, y, fill = NA)

# S4 method for class 'GRaster,SpatRaster'
extend(x, y, snap = "near", fill = NA)

# S4 method for class 'GRaster,SpatVector'
extend(x, y, snap = "near", fill = NA)

# S4 method for class 'GRaster,SpatExtent'
extend(x, y, snap = "near", fill = NA)

# S4 method for class 'GRaster,sf'
extend(x, y, snap = "near", fill = NA)

# S4 method for class 'GRaster,GSpatial'
extend(x, y, snap = "near", fill = NA)

Arguments

x

A GRaster.

y

Any of:

  • An object from which an extent can be obtained; i.e., a SpatRaster, SpatVector, SpatExtent, sf vector, or a GSpatial object (any of GRaster, GVector, or GRegion). If the extent of x is "outside" the extent of y on any side, the side(s) of x that are outside will be kept as-is (i.e., the extent of x will never be shrunk).

  • A single positive integer: Number of rows and columns to add to the top, bottom, and sides of the raster.

  • Two integers >= 0: Number of columns (1st value) to add to the sides, and number of rows (2nd value) to add to the top and bottom of the raster.

  • Four integers >= 0: Number of rows and columns to add (left column, right column, bottom row, top row).

fill

Numeric: Value to place in the new cells. The default is NA.

snap

Character: Method used to align y to x. Partial matching is used. This is only used if y is not a set of numbers.

  • "near" (default): Round to nearest row/column

  • "in": Round "inward" toward the extent of x to nearest row/column

  • "out": Round "outward" away from the extent of x to the nearest row/column.

Value

A GRaster.

Details

Known issues: When GRasters are saved to disk explicitly using writeRaster(), or implicitly using rast() or plot(), rows and columns that are entirely NA are dropped.

See also

terra::extend()

Examples

if (grassStarted()) {

# Setup
library(terra)

# Example data
madElev <- fastData("madElev")
madRivers <- fastData("madRivers")

# Send spatial objects to GRASS:
elev <- fast(madElev)
rivers <- fast(madRivers)

# Extend raster by number of rows/columns:
extended1 <- extend(elev, 10, fill = 900)
extended2 <- extend(elev, c(10, 20), fill = 900)
extended3 <- extend(elev, c(10, 80, 0, 100), fill = 900)
dim(elev)
dim(extended1)
dim(extended2)
dim(extended3)

plot(extended3)

# Note that when exporting a raster (including plotting it), NA rows and
# columns are removed.
extended4 <- extend(elev, 100, fill=1) # default fill is NA
extended4terra <- rast(extended4)

dim(extended4)
dim(extended4terra)

plot(extended4)

# Extend the raster by another object with a wider extent. We will crop the
# raster so that it is smaller than the object we use to extend it,
# then extend it.
elevCrop <- crop(elev, rivers)
uncrop <- extend(elevCrop, elev, fill = 900)
plot(uncrop)

}