NAME
r.null - The function of r.null is to explicitly create the
NULL-value bitmap file.
(GRASS 5 Raster Program)
SYNOPSIS
r.null
r.null -fincr
map=name
[setnull=val
[-val][,val[-val],...]]
[null=value]
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.
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 which validates all data cells.
- -r
- Remove NULL-value bitmap file.
Parameters:
- map
- raster map for which to edit null file
- setnull=range[,range...]
- The values specified in the ranges are 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.
- null=value
- Eliminate the NULL value and replace it with value.
This argument is applied only to existing NULL values, and not to the NULLs
created by the setnull argument.
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
Then he/she recodes this copy.
SEE ALSO
r.support
and
r.quant
AUTHOR
U.S.Army Construction Engineering
Research Laboratory
Last changed: $Date$