tiles: Divide a GRaster into spatially exclusive subsets

In adamlilith/fasterRaster: Faster Raster and Spatial Vector Processing Using 'GRASS GIS'

Divide a GRaster into spatially exclusive subsets

Description

This function divides a raster into "tiles" or spatial subsets which can be used for speeding some raster calculations. Tiles can be mutually exclusive or overlap by a user-defined amount.

Usage

## S4 method for signature 'GRaster'
tiles(x, n, overlap = 0, verbose = FALSE)

Arguments

x	A GRaster.
n	Numeric vector: Number of tiles to create. This can be a single number, in which case x is divided into n × n tiles, or two values in which case it is divided into n[1] × n[2] tiles (rows x columns).
overlap	Numeric vector (default is 0): Number of rows/columns by which to expand the size of tiles so they overlap. This can be a single value or two values. If just one is provided, the tiles will be expanded by overlap rows and overlaps columns. If two numbers are provided, the tiles will be expanded by overlap[1] rows and overlap[2] columns.
verbose	Logical: If TRUE, display progress. Default is FALSE.

Value

A list with one element per tile. The lapply() and sapply() functions can be used to apply functions to each tile in the list.

Examples

if (grassStarted()) {

# Setup
library(terra)

# Elevation raster
madElev <- fastData("madElev")

# Convert a SpatRaster to a GRaster:
elev <- fast(madElev)

# Create spatially exclusive tiles:
exclusive <- tiles(elev, n = 2, verbose = TRUE)

startpar <- par(mfrow = c(2, 3))
plot(elev, main = "Original")

for (i in seq_along(exclusive)) {
	plot(exclusive[[i]], ext = elev, main = paste("Tile", i))
}
par(startpar)

# Create tiles that overlap:
overlaps <- tiles(elev, n = 2, overlap = 200, verbose = TRUE)

startpar <- par(mfrow = c(2, 3))
plot(elev, main = "Original")

for (i in seq_along(overlaps)) {
	plot(overlaps[[i]], ext = elev, main = paste("Tile", i))
}
par(startpar)

}

adamlilith/fasterRaster documentation built on Oct. 26, 2024, 4:06 p.m.