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 21:09:06 +0200 (Fri, 16 May 2008) $
Full index
© 2003-2011 GRASS Development Team