fasterRaster (version 8.4.1.0)

zonalGeog,GRaster-method: Geographic statistics for sets of cells with the same values

Description

This function calculates geographic statistics for each set of cells in an integer or factor GRaster. Statistics include:

• Area

• Perimeter length

• "Compact square" statistic: $4\sqrt{(}area)/perimeter)$

• "Compact circle" statistic: $4\ast P/(2\sqrt{(}\pi \ast A))$ where P is the perimeter length and A the area.

• fractal dimension: $2(log(P)/log(A+0.001))$ where P is perimeter length and A is area.

• The average x- and y-coordinates of each zone.

Usage

# S4 method for GRaster
zonalGeog(x, unit = "meters")

Value

A list of data.frames or a data.tables, one per layer in x. Only layers that are integers or factors have their geographies calculated. Other layers have NULL tables returned.

Arguments

x

A GRaster.

unit

Character: Units of the output. Any of:

• "meters" (default)

• "kilometers" or "km"

• "miles" or "mi"

• "yards" or "yd"

• "feet" or "ft": International foot; 1 foot exactly equal to 0.3048 meters

• "cells": Number or cells

Partial matching is used and case is ignored.

Examples

if (grassStarted()) {

# Setup
library(terra)

# Example data: Elevation and land cover
madElev <- fastData("madElev")
madForest2000 <- fastData("madForest2000")
madCover <- fastData("madCover")

# Convert to GRasters:
elev <- fast(madElev)
forest2000 <- fast(madForest2000)
cover <- fast(madCover)

# Rename
names(elev) <- "elev"
names(forest2000) <- "forest"

# Geometric statistics for an integer raster zoned by elevation:
fun <-
  "= if (elev <400 & forest == 1, 0, if (elev >=400 & forest == 1, 1, null()))"
forestByElev <- app(c(elev, forest2000), fun = fun)
plot(forestByElev, main = "forest < 400 m & >= 400 m")
zonalGeog(forestByElev)

# Geometric statistics for a categorical raster:
zonalGeog(cover)

}