r.recode - GRASS manual
Author: GRASS Development Team
Description: r.recode: Recodes categorical raster maps.
Keywords: raster, recode categories, reclassification

## 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)

Latest change: Thursday May 08 20:58:05 2025 in commit: 4144ba81fa125e1549fc52e1cf5feb4fa004be8b

Main index | Raster index | Topics index | Keywords index | Graphical index | Full index

© 2003-2026 GRASS Development Team, GRASS 8.6.0dev Reference Manual