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r.mask(1)		    GRASS GIS User's Manual		     r.mask(1)

NAME
       r.mask  - Creates a MASK	for limiting raster operation.

KEYWORDS
       raster, mask

SYNOPSIS
       r.mask
       r.mask --help
       r.mask	[-ir]	 [raster=name]	   [maskcats=string]	 [vector=name]
       [layer=string]	  [cats=range]	   [where=sql_query]	 [--overwrite]
       [--help]	 [--verbose]  [--quiet]	 [--ui]

   Flags:
       -i
	   Create inverse mask

       -r
	   Remove existing mask	(overrides other options)

       --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:
       raster=name
	   Name	of raster map to use as	mask

       maskcats=string
	   Raster values to use	for mask
	   Format: 1 2 3 thru 7	*
	   Default: *

       vector=name
	   Name	of vector map to use as	mask
	   Or data source for direct OGR access

       layer=string
	   Layer number	or name	(vector)
	   Vector  features can	have category values in	different layers. This
	   number determines which layer to use. When used with	direct OGR ac-
	   cess	this is	the layer name.
	   Default: 1

       cats=range
	   Category values (vector)
	   Example: 1,3,7-9,13

       where=sql_query
	   WHERE conditions of SQL statement without 'where' keyword (vector)
	   Example: income < 1000 and population >= 10000

DESCRIPTION
       r.mask  - Facilitates creation of a raster "MASK" map to	control	raster
       operations.

       The MASK	is only	applied	when reading an	existing GRASS raster map, for
       example when used in a module as	an input map.  The MASK	will block out
       certain areas of	a raster map from analysis and/or display, by "hiding"
       them  from sight	of other GRASS modules.	Data falling within the	bound-
       aries of	the MASK can be	modified and  operated	upon  by  other	 GRASS
       raster  modules;	data falling outside the MASK is treated as if it were
       NULL.

       Because the MASK	is actually only a reclass map named "MASK", it	can be
       copied,	renamed,  removed, and used in analyses, just like other GRASS
       raster map layers.  The user should be aware that  a  MASK  remains  in
       place  until  a	user renames it	to something other than	"MASK",	or re-
       moves it	using "r.mask -r" or g.remove.

       Grid cells in the MASK map containing 0 or NULL will replace data  with
       NULL,  while  cells  containing	other  values  will allow data to pass
       through unaltered.

       To restore raster operations to normal (i.e., all cells of the  current
       region),	 remove	 the  MASK file	by setting the -r remove MASK flag. In
       this case, a dummy value	must also be given for the input parameter.  A
       MASK  also  can	be  removed by using g.remove or by renaming it	to any
       other name with g.rename.

NOTES
       The above method	for specifying a  "mask"  may  seem  counterintuitive.
       Areas  inside  the  MASK	are not	hidden;	areas outside the MASK will be
       ignored until the MASK file is removed.

       The MASK	is read	as an integer  map.  If	 MASK  is  actually  a	float-
       ing-point map, the values will be converted to integers using the map's
       quantisation rules (this	 defaults  to  round-to-nearest,  but  can  be
       changed with r.quant).

       r.mask  uses  r.reclass	to  create  a  reclassification	of an existing
       raster map and name it MASK. A reclass map takes	up less	space, but  is
       affected	 by  any  changes to the underlying map	from which it was cre-
       ated.  The user can select category values from the input raster	to use
       in the MASK with	the maskcats parameter;	if r.mask is run from the com-
       mand line, the category values listed in	maskcats must be  quoted  (see
       example below).

       Somewhat	 similar program functions to those performed by r.mask	can be
       done using r.mapcalc, g.region, and other commands.

EXAMPLES
       The examples are	based on the North Carolina sample dataset.

       Create a	raster mask, for contraining  the  calculation	of  univariate
       statistics of the elevation values for "lakes":
       # set computation region	to lakes raster	map
       g.region	raster=lakes -p
       # use lakes as MASK
       r.mask raster=lakes
       # get statistics	for elevation pixels of	lakes:
       r.univar	elevation
       Remove the raster mask ("MASK" map) with	the -r flag:
       r.mask -r
       Creating	 a  mask from selected categories in the North Carolina	'geol-
       ogy_30m'	raster map:
       g.region	raster=geology_30m -p
       r.category geology_30m
       d.mon wx0
       d.rast geology_30m
       r.mask raster=geology_30m maskcats="217 thru 720"
       d.mon wx0
       d.rast geology_30m

SEE ALSO
	g.region, r.mapcalc, r.reclass,	g.remove, g.rename

AUTHOR
       Michael Barton, Arizona State University

SOURCE CODE
       Available at: r.mask source code	(history)

       Main index | Raster index | Topics index	| Keywords index  |  Graphical
       index | Full index

       A(C) 2003-2020 GRASS Development	Team, GRASS GIS	7.8.4 Reference	Manual

GRASS 7.8.4							     r.mask(1)

NAME | KEYWORDS | SYNOPSIS | DESCRIPTION | NOTES | EXAMPLES | SEE ALSO | AUTHOR | SOURCE CODE

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