r.null(1)

1r.null(1)                     Grass User's Manual                    r.null(1)
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NAME

6       r.null  - Creates explicitly the NULL-value bitmap file.
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KEYWORDS

9       raster
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SYNOPSIS

12       r.null
13       r.null help
14       r.null    [-fincr]    map=string    [setnull=val[-val][,val[-val],...]]
15       [null=float]   [--verbose]  [--quiet]
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17   Flags:
18       -f
19           Only do the work if the map is floating-point
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21       -i
22           Only do the work if the map is integer
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24       -n
25           Only do the work if the map doesn't have a NULL-value bitmap file
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27       -c
28           Create NULL-value bitmap file validating all data cells
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30       -r
31           Remove NULL-value bitmap file
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33       --verbose
34           Verbose module output
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36       --quiet
37           Quiet module output
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39   Parameters:
40       map=string
41           Raster map for which to edit null file
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43       setnull=val[-val][,val[-val],...]
44           List of cell values to be set to NULL
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46       null=float
47           The value to replace the null value by
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DESCRIPTION

50       The function of r.null is to explicitly create  the  NULL-value  bitmap
51       file.  The  intended usage is to fix "old" maps that don't have a NULL-
52       value bitmap file (i.e. to indicate if zero is valid value or is to  be
53       converted to NULL). The module does not work with reclassified maps.
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55       The  design is flexible. Ranges of values can be set to NULL and/or the
56       NULL value can be eliminated and replace with a specified value.
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58       The setnull parameter is used to specify values in the ranges to be set
59       to  NULL.   A  range is either a single value (e.g., 5.3), or a pair of
60       values (e.g., 4.76-34.56).  Existing NULL-values are left NULL,  unless
61       the null argument is requested.
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63       The  null  parameter  eliminates  the  NULL  value and replaces it with
64       value. This argument is applied only to existing NULL values,  and  not
65       to the NULLs created by the setnull argument.
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EXAMPLES

68       Set specific values of a classified map to NULL:
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70       r.null map=landcover.30m setnull=21,22
71        Set NULL-values of a map to a specific value:
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73       r.null map=fields null=99
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NOTES

77       Note that value is restricted to integer if the map is an integer map.
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79       r.null and reclassified maps:
80       The  problem is, if r.null was run on the reclass raster it would alter
81       the original and any other reclass rasters of the original.   Therefore
82       r.null   doesn't   allow  to  recode  reclassified  maps  (products  of
83       r.reclass).
84       So, the way to recode such a map is: The user makes a raster out of the
85       reclass that isn't a reclass by copying it:
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87       r.mapcalc newmap = reclass
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AUTHOR

94       U.S.Army Construction Engineering Research Laboratory
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96       Last changed: $Date: 2006-01-06 10:31:35 +0100 (Fri, 06 Jan 2006) $
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98       Full index
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100       © 2003-2008 GRASS Development Team
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104GRASS 6.3.0                                                          r.null(1)