init: GRaster with values equal to row, column, coordinate,...

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

GRaster with values equal to row, column, coordinate, regular, or "chess"

Description

This function can be used to make a GRaster with cell values equal to the cell center's longitude, latitude, row, or column, or in a "chess"-like or "regular" pattern.

Usage

## S4 method for signature 'GRaster'
init(x, fun, odd = TRUE, vals = c(0, 1))

Arguments

x	A GRaster to be used as a template.
fun	Character: Any of: "x" or "y": Cell longitude or latitude "row" or "col": Cell row or column "chess": Alternating values. "regular": Evenly-spaced cells with the same value.
odd	Logical: If TRUE (default), and fun is "chess", then the top left cell in the raster will be a "negative" cell. If FALSE, then the top left cell with be "positive".
vals	Vector of two numeric values: If fun is "chess" or "regular", then assign the first value to "positive" cells and the second value to "negative" cells. The default is c(1, 0)

Value

A GRaster with as many layers as x.

See Also

terra::init(), longlat()

Examples

if (grassStarted()) {

# Setup
library(terra)

# Elevation raster, rivers vector
madElev <- fastData("madElev")

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

# Cell coordinates
init(elev, "x")
init(elev, "y")

# Cell row or column
init(elev, "row")
init(elev, "col")

# Chess
elevAgg <- aggregate(elev, 32) # make cells bigger so we can see

chessOdd <- init(elevAgg, "chess")
chessEven <- init(elevAgg, "chess", odd = FALSE)

chess <- c(chessOdd, chessEven)
names(chess) <- c("odd", "even")
plot(chess)

# Chess with user-defined values
elevAgg <- aggregate(elev, 32) # make cells bigger so we can see

chessOdd13 <- init(elevAgg, "chess", vals = c(0, 13))
chessEven13 <- init(elevAgg, "chess", odd = FALSE, vals = c(0, 13))

chess13 <- c(chessOdd13, chessEven13)
names(chess13) <- c("odd", "even")
plot(chess13)

# Regular
elevAgg <- aggregate(elev, 32) # make cells bigger so we can see

regOdd <- init(elevAgg, "regular")
regEven <- init(elevAgg, "regular", odd = FALSE)

reg <- c(regOdd, regEven)
names(reg) <- c("odd", "even")
plot(reg)

}

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