r.recode(1)

NAME
r.recode - Recodes categorical raster maps.

KEYWORDS
raster, recode categories, reclassification

SYNOPSIS
r.recode
r.recode --help
r.recode [-ad] input=name output=name rules=name [title=string] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

  Flags:

-a
    Align the current region to the input raster map

-d
    Force output to ’double’ raster map type (DCELL)

--overwrite
    Allow output files to overwrite existing files

--help
    Print usage summary

--verbose
    Verbose module output

--quiet
    Quiet module output

--ui
    Force launching GUI dialog

  Parameters:

input=name [required]
    Name of raster map to be recoded

output=name [required]
    Name for output raster map

rules=name [required]
    File containing recode rules
    ’-’ for standard input

title=string
    Title for output raster map

DESCRIPTION
r.recode creates an output raster map by recoding input raster map based on recode rules. A title for the output raster map may be (optionally) specified by the user.

The recode rules can be read from standard input (i.e., from the keyboard, redirected from a file, or piped through another program) by entering rules=-.

Rules are defined in one of these formats:

old_low:old_high:new_low:new_high
old_low:old_high:new_val  (i.e. new_high == new_low)
*:old_val:new_val         (interval [inf, old_val])
old_val:*:new_val         (interval [old_val, inf])

r.recode is loosely based on r.reclass and uses the GRASS Reclass Library to convert the rasters. It has routines for converting to every possible combination of raster (eg. CELL to DCELL, DCELL to FCELL, etc). Standard floating point raster precision is float (FCELL), with -d double precision (DCELL) will be written.

There are four basic routines that it accepts:

1   old-low to old-high is reclassed to new-low to new high , where the user provides all four values. The program figures on the fly what type of raster should be created.

2   old-low to old-high is reclassed to a single new value. Anything outside the range is null.

3   * to old-high will reclass everything less than old-high to a single new value.

4   old-low to * will reclass everything greater than old-low to a single new value.

These four sets of arguments can be given on the command line, or piped via stdin or a file. More than one set of arguments is accepted.

EXAMPLES

  Map type conversion
To simply convert a raster between formats (eg. int to float) the user would use the first argument. For example

10:1500:0.1:15.0

would convert an input raster map with range between 10 and 1500 to a float raster raster with range between 0.1 and 15.0.

  Value replacement
r.recode can be used to replace existing cell values by others. The formatting is as described above. In following example the values 1, 2 and 3 are replaced by 1.1, 7.5 resp. 0.4:

r.recode input=oldmap output=newmap rules=- << EOF
1:1:1.1:1.1
2:2:7.5:7.5
3:3:0.4:0.4
EOF

SEE ALSO
r.reclass

AUTHOR
CERL

SOURCE CODE

Available at: r.recode source code (history)

Accessed: Saturday May 09 11:16:28 2026

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