trusty (1) r.null.1grass.gz

NAME

       r.null  - Manages NULL-values of given raster map.

KEYWORDS

       raster, null data

SYNOPSIS

       r.null
       r.null help
       r.null [-fincr] map=name  [setnull=val[-val][,val[-val],...]]   [null=float]   [--verbose]  [--quiet]

   Flags:
       -f
           Only do the work if the map is floating-point

       -i
           Only do the work if the map is integer

       -n
           Only do the work if the map doesn't have a NULL-value bitmap file

       -c
           Create NULL-value bitmap file validating all data cells

       -r
           Remove NULL-value bitmap file

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       map=name
           Name of raster map for which to edit null file

       setnull=val[-val][,val[-val],...]
           List of cell values to be set to NULL

       null=float
           The value to replace the null value by

DESCRIPTION

       The  function  of r.null is to explicitly create the NULL-value bitmap file. The intended usage is to fix
       "old" maps that don't have a NULL-value bitmap file (i.e. to indicate if zero is valid value or is to  be
       converted to NULL). The module does not work with reclassified maps.

       The  design  is flexible. Ranges of values can be set to NULL and/or the NULL value can be eliminated and
       replace with a specified value.

       The setnull parameter is used to specify values in the ranges to be set to NULL.  A  range  is  either  a
       single  value  (e.g.,  5.3), or a pair of values (e.g., 4.76-34.56).  Existing NULL-values are left NULL,
       unless the null argument is requested.

       The null parameter eliminates the NULL value and replaces it with value. This argument is applied only to
       existing NULL values, and not to the NULLs created by the setnull argument.

EXAMPLES

       Set specific values of a classified map to NULL:

       r.null map=landcover.30m setnull=21,22
        Set NULL-values of a map to a specific value:

       r.null map=fields null=99

NOTES

       Note that value is restricted to integer if the map is an integer map.

       r.null and reclassified maps:
       The problem is, if r.null was run on the reclass raster it would alter the original and any other reclass
       rasters of the original.  Therefore r.null  doesn't  allow  to  recode  reclassified  maps  (products  of
       r.reclass).
       So,  the  way to recode such a map is: The user makes a raster out of the reclass that isn't a reclass by
       copying it:

       r.mapcalc newmap = reclass

SEE ALSO

       r.support and r.quant

AUTHOR

       U.S.Army Construction Engineering Research Laboratory

       Last changed: $Date: 2008-05-16 12:09:06 -0700 (Fri, 16 May 2008) $

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       © 2003-2013 GRASS Development Team