GRASS GIS manual: r.clump

Note: A new GRASS GIS stable version has been released: GRASS GIS 7.4, available here.
Updated manual page: here

NAME

r.clump - Recategorizes data in a raster map by grouping cells that form physically discrete areas into unique categories.

KEYWORDS

raster, statistics, reclass, clumps

SYNOPSIS

r.clump

r.clump --help

r.clump [-dg] input=name [output=name] [title=string] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-d: Clump also diagonal cells; Clumps are also traced along diagonal neighboring cells
-g: Print only the number of clumps in shell script style
--overwrite: Allow output files to overwrite existing files
--help: Print usage summary
--verbose: Verbose module output
--quiet: Quiet module output
--ui: Force launching GUI dialog

Parameters:

input=name [required]: Name of input raster map
output=name: Name for output raster map
title=string: Title for output raster map

DESCRIPTION
NOTES
EXAMPLES
SEE ALSO
AUTHOR

DESCRIPTION

r.clump finds all areas of contiguous cell category values in the input raster map. NULL values in the input are ignored. It assigns a unique category value to each such area ("clump") in the resulting output raster map.

Category distinctions in the input raster map are preserved. This means that if distinct category values are adjacent, they will NOT be clumped together. The user can run r.reclass prior to r.clump to recategorize cells and reassign cell category values.

NOTES

By default, the resulting clumps are connected only by their four direct neighbors (left, right, top, bottom). The -d flag activates also diagonal clump tracing.

r.clump works properly with raster map that contains only "fat" areas (more than a single cell in width). Linear elements (lines that are a single cell wide) may or may not be clumped together depending on the direction of the line - horizontal and vertical lines of cells are considered to be contiguous, but diagonal lines of cells are not considered to be contiguous and are broken up into separate clumps unless the -d flag is used.

A random color table and other support files are generated for the output raster map.

EXAMPLES

Perform clumping on "lakes" map (North Carolina sample dataset) and report area sizes for each lake individually rather by waterbody type:

g.region raster=lakes -p

# report sizes by waterbody type
r.report lakes units=h

# clump per raster polygon
r.clump lakes out=lakes_individual

# report sizes by individual waterbody
r.report lakes_individual units=h

AUTHOR

Michael Shapiro, U.S. Army Construction Engineering Research Laboratory
Markus Metz (diagonal clump tracing)

Last changed: $Date: 2014-12-19 13:55:37 -0800 (Fri, 19 Dec 2014) $

SOURCE CODE

Available at: r.clump source code (history)