NAME

r.recode - recode raster maps
(GRASS Raster Program)

SYNOPSIS

r.recode [-ad] input=name output=name [title=name]

DESCRIPTION

r.recode creates an output map layer based on an input raster map layer. The output map layer will be a recoding of the input map layer based on recode rules input to r.recode. A title for the output map layer may be (optionally) specified by the user.

The recode rules are read from standard input (i.e., from the keyboard, redirected from a file, or piped through another program).

The program will be run non-interactively if the user specifies the name of the raster map layer to be recoded, the name of an output layer to hold recoded map, and (optionally) the name of a title for the output map.

Flag:

-a
Align the current region to the input map
-d
Force output to double map type (DCELL)

Parameters:

input
Raster map to be recoded
output
Name for the resulting raster map
title
Title for the resulting raster map
Enter a rule 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. int to double, double to float, etc). Standard floating point raster precision is float, with -d double precision 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 old raster with range between 10 and 1500 to a float 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 in=oldmap out=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: 2002/03/01 00:27:45 $