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]
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17   Flags:
18       -f  Only do the work if the map is floating-point
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20       -i  Only do the work if the map is integer
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22       -n  Only do the work if the map doesn't have a NULL-value bitmap file
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24       -c  create NULL-value bitmap file validating all data cells
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26       -r  remove NULL-value bitmap file
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28   Parameters:
29       map=string
30           Raster map for which to edit null file
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32       setnull=val[-val][,val[-val],...]
33           List of cell values to be set to NULL
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35       null=float
36           The value to replace the null value by
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DESCRIPTION

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

57       Set specific values of a classified map to NULL:
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59       r.null map=landcover.30m setnull=21,22
60        Set NULL-values of a map to a specific value:
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62       r.null map=fields null=99
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NOTES

66       Note that value is restricted to integer if the map is an integer map.
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68       r.null and reclassified maps:
69       The  problem is, if r.null was run on the reclass raster it would alter
70       the original and any other reclass rasters of the original.   Therefore
71       r.null   doesn't   allow  to  recode  reclassified  maps  (products  of
72       r.reclass).
73       So, the way to recode such a map is: The user makes a raster out of the
74       reclass that isn't a reclass by copying it:
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76       r.mapcalc newmap = reclass
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AUTHOR

83       U.S.Army Construction Engineering Research Laboratory
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85       Last changed: $Date: 2006/01/06 09:31:35 $
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87       Full index
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91GRASS 6.2.2                                                          r.null(1)