NAME

v.extract - Selects vector objects from an existing vector map and creates a new map containing only the selected objects.

SYNOPSIS

v.extract
v.extract help
v.extract [-dt] input=string output=string [type=string[,string,...]] [field=integer] [new=integer] [list=string[,string,...]] [file=string] [where=string]

Flags:

-d
Dissolve common boundaries (default is no)
-t
Do not copy table.

Parameters:

input=string
Name of input vector
output=string
Name of output vector
type=string
Select type: point, line, boundary, centroid or area
Options: point,line,boundary,centroid,area,face
Default: point,line,boundary,centroid,area,face
field=integer
Field value
Default: 1
new=integer
Enter -1 to keep original category or a desired NEW category value. If new <> 0, table is not copied.
Default: 1
list=string
Category ranges: e.g. 1,3-8,13
file=string
Text file with category numbers/number ranges
where=string
WHERE conditions of SQL statement without 'where' keyword. (example: income < 1000 and inhab >= 10000)

DESCRIPTION

v.extract allows a user to select vector objects from an existing vector map and creates a new map containing only the selected objects. Database tables can be queried with SQL statements, if a connection is established. Dissolving (optional) is based on the output categories. If 2 adjacent areas have the same output category, the boundary is removed.

EXAMPLES

v.extract -d list=1,2,3,4 input=soils output=soil_groupa type=area new=1

Produces a new vector area file soil_groupa containing 'area' boundaries from soils with area category numbers of 1 thru 4; any common boundaries are dissolved, and all areas of the new map will be assigned category number 1.

v.extract -d list=Abc,Def1,12A,WWd input=soils output=soil_groupa type=area new=0

Produces a new vector area file soil_groupa containing 'area' boundaries from soils with area category labels of Abc,Def1, 12A,WWd; these labels correspond to numbers 1 thru 4 of soils. Any common boundaries are dissolved, all areas of the new map will be retain their original category numbers 1 thru 4, in this case, since new was set to 0.

v.extract input=soils output=soil_groupa type=area new=1 file=sample

Produces a new vector area file soil_groupa containing 'area' boundaries from soils. No common boundaries are dissolved, all areas of the new map will be assigned category number 1. The "labels" (-n option) can be found in the file sample of the current directory.

v.extract input=markveggy.shp output=markveggy.1 new=1 where="(VEGTYPE = 'Wi') or (VEGTYPE = 'PS') or (PRIME_TYPE='Wi')"

Produces a new vector map with category label 1 if the SQL statement is fulfilled.

SEE ALSO

GRASS 5.7 tutorial pages

AUTHOR

R.L. Glenn, USDA, SCS, NHQ-CGIS

Last changed: $Date: 2004/06/17 07:53:54 $


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