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

SEE ALSO

r.average, r.buffer, r.distance, r.grow r.mapcalc, r.mfilter, r.neighbors, r.to.vect, r.reclass, r.statistics, r.support

AUTHOR

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

Last changed: $Date$