v.reclass(1grass)

NAME
v.reclass - Changes vector category values for an existing vector map according to results of SQL queries or a value in attribute table column.

KEYWORDS
vector, reclassification, attributes

SYNOPSIS
v.reclass
v.reclass --help
v.reclass input=name [layer=string] [type=string[,string,...]] output=name [column=name] [rules=name] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

  Flags:

--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 input vector map
    Or data source for direct OGR access

layer=string
    Layer number or name
    Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.
    Default: 1

type=string[,string,...]
    Input feature type
    Options: point, line, boundary, centroid
    Default: point,line,boundary,centroid

output=name [required]
    Name for output vector map

column=name
    The name of the column whose values are to be used as new categories
    The source for the new key column must be type integer or string

rules=name
    Full path to the reclass rule file

DESCRIPTION
v.reclass allows user to create a new vector map based on the reclassification of an existing vector map. It also allows the user to change the key column away from the default of "cat" with the column option.

Rules file may contain on each row either pair:

keyword value

(separated by space) or comment beginning with ’#’ (hash). Definition of new category begins with keyword cat followed by the new category value. Keyword where specifies SQL where condition.

NOTES
No table is created for the reclassed map if the column option is used and the column type is integer (as the result could contain ambiguities). If the column option is used and the column type is string, a new table is created containing the newly generated cat numbers and a single column containing the unique string column values, sorted in alphabetical order.

For dissolving common boundaries, see v.dissolve.

Either the rules or column option must be specified.

EXAMPLES

  Example 1: Reclass by rules

v.reclass input=land output=land_u type=boundary rules=land.rcl

The rules file contains:

# land reclass file
cat 1
where use = ’E13’ and owner = ’Jara Cimrman’
cat 2
where use = ’E14’

Produces a new vector area map land_u containing boundaries from land with area category values selected from database by SQL select statement:
select id from tland where use = ’E13’ and owner = ’Jara Cimrman’ changed to category 1;
values selected from database by SQL select statement:
select id from tland where use = ’E14’ changed to category 2.

  Example 2: Reclass by attribute column
(North Carolina sample dataset)

v.reclass in=streams out=streams_by_type column=I_vs_P
v.db.select streams_by_type
cat|I_vs_P
1|intermittent
2|perennial

KNOWN ISSUES
No table is created for reclassed layer if the rules option is used.

SEE ALSO
v.dissolve, v.extract

GRASS SQL interface

AUTHORS
R.L. Glenn, USDA, SCS, NHQ-CGIS
from v.reclass to v.db.reclass and later to v.reclass in 5.7 rewritten by Radim Blazek

SOURCE CODE

Available at: v.reclass source code (history)

Accessed: Thursday Oct 30 22:18:16 2025

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