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NAME

r.recode - Recodes categorical raster maps.

KEYWORDS

raster, recode category

SYNOPSIS

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

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
--verbose
Verbose module output
--quiet
Quiet module output

Parameters:

input=name
Name of raster map to be recoded
output=name
Name for output raster map
rules=name
File containing recode rules
"-" to read from stdin
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 bewteen 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 << EOF
    1:1:1.1:1.1
    2:2:7.5:7.5
    3:3:0.4:0.4
EOF

AUTHOR

CERL

Last changed: $Date: 2010-10-31 01:50:58 -0700 (Sun, 31 Oct 2010) $

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