clump: Group adjacent cells with similar values

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

Group adjacent cells with similar values

Description

clump() identifies groups of adjacent cells that have the same value or same approximate value, and assigns them a unique number, creating "clumps" of same- or similar-valued cells.

Usage

## S4 method for signature 'GRaster'
clump(x, minDiff = 0, minClumpSize = 1, diagonal = TRUE)

Arguments

x	A GRaster.
minDiff	Numeric in the range [0, 1): Minimum difference between cells in order for them to be assigned to the same clump. This is a proportion of the range across all cells. For example, if minDiff is set to 0.01, then the maximum difference between cells in a clump can be up to 1% of the entire range across all cells. Small values can create large clumps. The default is 0, in which case values have to be exactly the same.
minClumpSize	Numeric integer >= 1. Minimum number of cells in a clump. The default is 1.
diagonal	Logical: If TRUE (default), then cells "connected" at corners will be included as part of the same clump.

Value

A GRaster.

Examples

if (grassStarted()) {

# Setup
library(sf)
library(terra)

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

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

# Find clumps based on exact values. This will appear as a gradient because
# most cells are assigned to a group of 1 cell.
exact <- clump(elev)
plot(exact)

# Clump based on approximate values:
approx <- clump(elev, minDiff = 0.0075)
plot(approx)

# Clump based on approximate values with minimum clump size
# (this can take a minute or two):
approx20 <- clump(elev, minDiff = 0.005, minClumpSize = 20)
plot(approx20)

approx
approx20

}

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