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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[,name,...]   [output=name]    [title=string]    [threshold=float]
       [minsize=integer]   [--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[,name,...] [required]
           Name of input raster map(s)

       output=name
           Name for output raster map

       title=string
           Title for output raster map

       threshold=float
           Threshold to identify similar cells
           Valid range: 0 = identical to < 1 = maximal difference
           Default: 0

       minsize=integer
           Minimum clump size in cells
           Clumps smaller than minsize will be merged to form larger clumps
           Default: 1

DESCRIPTION

       r.clump  finds  all areas of contiguous cell category values (connected components) 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.

       r.clump  can  also perform "fuzzy" clumping where neighboring cells that are not identical
       but similar to each other are clumped together. Here, the spectral  distance  between  two
       cells is scaled to the range [0, 1] and compared to the threshold value. Cells are clumped
       together if their spectral distance is &#8804; threshold. The result is very sensitive  to
       this  threshold  value,  a  recommended start value is 0.01, then increasing or decreasing
       this value  according  to  the  desired  output.   Once  a  suitable  threshold  has  been
       determined, noise can be reduced by merging small clumps with the minsize option.

       r.clump  can  also  use multiple raster maps of any kind (CELL, FCELL, DCELL) as input. In
       this case, the spectral distance between cells is used to determine the similarity of  two
       cells. This means that input maps must be metric: the difference cell 1 - cell 2 must make
       sense. Categorical maps, e.g. land cover, can not be used  in  this  case.   Examples  for
       valid inpat maps are satellite imagery, vegetation indices, elevation, climatic parameters
       etc.

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

       Perform fuzzy clumping on Landsat 7 2002 imagery (North Carolina sample dataset)
       g.region raster=lsat7_2002_10 -p
       r.clump in=lsat7_2002_10,lsat7_2002_20,lsat7_2002_30,lsat7_2002_40,lsat7_2002_50,lsat7_2002_70 \
               out=lsat7_2002_clump threshold=0.045
       # reduce noise
       r.clump in=lsat7_2002_10,lsat7_2002_20,lsat7_2002_30,lsat7_2002_40,lsat7_2002_50,lsat7_2002_70 \
               out=lsat7_2002_clump_min10 threshold=0.045 minsize=10

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, fuzzy clumping)

       Last changed: $Date: 2016-07-15 15:14:26 +0200 (Fri, 15 Jul 2016) $

SOURCE CODE

       Available at: r.clump source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.6.1 Reference Manual