zonalGeog: Geographic statistics for sets of cells with the same values

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

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 * P / ( 2 \sqrt(\pi * 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 signature 'GRaster'
zonalGeog(x, unit = "meters")

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.

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.

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)

}

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