.TH v.category 1grass "" "GRASS 7.8.5" "GRASS GIS User's Manual"
.SH NAME
\fI\fBv.category\fR\fR  \- Attaches, deletes or reports vector categories to/from/of map geometry.
.SH KEYWORDS
vector, category, layer
.SH SYNOPSIS
\fBv.category\fR
.br
\fBv.category \-\-help\fR
.br
\fBv.category\fR [\-\fBgt\fR] \fBinput\fR=\fIname\fR  [\fBlayer\fR=\fIstring\fR[,\fIstring\fR,...]]   [\fBtype\fR=\fIstring\fR[,\fIstring\fR,...]]   [\fBids\fR=\fIrange\fR]   [\fBoutput\fR=\fIname\fR]  \fBoption\fR=\fIstring\fR  [\fBcat\fR=\fIinteger\fR]   [\fBstep\fR=\fIinteger\fR]   [\-\-\fBoverwrite\fR]  [\-\-\fBhelp\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR]  [\-\-\fBui\fR]
.SS Flags:
.IP "\fB\-g\fR" 4m
.br
Shell script style, currently only for report
.br
Format: layer type count min max
.IP "\fB\-t\fR" 4m
.br
Do not copy attribute table(s)
.IP "\fB\-\-overwrite\fR" 4m
.br
Allow output files to overwrite existing files
.IP "\fB\-\-help\fR" 4m
.br
Print usage summary
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.IP "\fB\-\-ui\fR" 4m
.br
Force launching GUI dialog
.SS Parameters:
.IP "\fBinput\fR=\fIname\fR \fB[required]\fR" 4m
.br
Name of input vector map
.br
Or data source for direct OGR access
.IP "\fBlayer\fR=\fIstring[,\fIstring\fR,...]\fR" 4m
.br
Layer number or name
.br
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.
.br
Default: \fI1\fR
.IP "\fBtype\fR=\fIstring[,\fIstring\fR,...]\fR" 4m
.br
Input feature type
.br
Options: \fIpoint, line, boundary, centroid, area, face, kernel\fR
.br
Default: \fIpoint,line,centroid,face\fR
.IP "\fBids\fR=\fIrange\fR" 4m
.br
Feature ids (by default all features are processed)
.br
Example: 1,3,7\-9,13
.IP "\fBoutput\fR=\fIname\fR" 4m
.br
Name for output vector map
.IP "\fBoption\fR=\fIstring\fR \fB[required]\fR" 4m
.br
Action to be done
.br
Options: \fIadd, del, chlayer, sum, report, print, layers, transfer\fR
.br
\fBadd\fR: add a category to features without category in the given layer
.br
\fBdel\fR: delete category (cat=\-1 to delete all categories of given layer)
.br
\fBchlayer\fR: change layer number (e.g. layer=3,1 changes layer 3 to layer 1)
.br
\fBsum\fR: add the value specified by cat option to the current category value
.br
\fBreport\fR: print report (statistics), in shell style: layer type count min max
.br
\fBprint\fR: print category values, layers are separated by \(cq|\(cq, more cats in the same layer are separated by \(cq/\(cq
.br
\fBlayers\fR: print only layer numbers
.br
\fBtransfer\fR: copy values from one layer to another (e.g. layer=1,2,3 copies values from layer 1 to layer 2 and 3)
.IP "\fBcat\fR=\fIinteger\fR" 4m
.br
Category value
.br
Default: \fI1\fR
.IP "\fBstep\fR=\fIinteger\fR" 4m
.br
Category increment
.br
Default: \fI1\fR
.SH DESCRIPTION
\fIv.category\fR attaches, copies, deletes or reports categories to/from/of
vector geometry objects. Further on, \fIv.category\fR adds a number
given by the \fIcat\fR option to categories of the selected layer.
These categories (IDs) are used to assign IDs or to group geometry objects
into categories (several different geometry objects share the same
category). These categories are also used to link geometry
object(s) to attribute records (from an attribute table linked to vector map).
.SH NOTES
Use \fIv.to.db\fR to upload related categories
to a linked attribute table.
.PP
The \fBtype\fR parameter specifies the type of geometry objects to which
the category is added; it is similar to an input filter \- only the
geometry specified in \(cqtype\(cq is processed.
.PP
If the \fBtype\fR parameter is set to \fBcentroid\fR and
the \fBoption\fR parameter set to \fBadd\fR, new categories will be
added to existing centroids. Note however, that new centroids cannot
be created this way.  To do so, they must be added manually
using \fIwxGUI vector
digitizer\fR or by running \fIv.category\fR with the type
parameter set to area.
.PP
If categories are copied with \fIoption=transfer\fR, a warning is
issued if categories already exit in the layer they are copied to. In
this case the user must make sure beforehand that copying categories
from one layer to another layer does not cause undesired grouping of
different geometry objects into the same categories. This can be avoided
by specifying only one \fIlayer\fR. The module will then find the
next free layer number and copy categories to there. The new layer number
is reported at the end.
.PP
Areas are a special case because it is impossible to attach a cat to
an area without a centroid; in this case, the module places new
centroids in areas automatically for \fBtype=area\fR.
.PP
The \fBcat\fR parameter is only used with \fBoption\fR=\fIadd\fR,
\fBoption\fR=\fIsum\fR and \fBoption\fR=\fIdel\fR.
.PP
Categories can be deleted for the given layer with \fIoption=del\fR.
If \fBcat\fR is set to \fI\-1\fR, all categories for the given layer
are deleted. If \fBcat\fR is zero or positive, only this category value
will be deleted. By default, \fBcat\fR is set to \fI1\fR which means
that only categories of value \fI1\fR will be deleted.
.PP
With \fBoption=report\fR, the module reports for each layer and
type the total number of categories, the minimum and the maximum
category number. If there are e.g. two lines with line 1 having
category 1 and line 1 having categories 1 and 2, then there are a total
of three category values with minimum 1 and maximum 2.
.PP
The \fBids\fR parameter specifies the list of feature IDs to which the
operation is performed; by default, all vector feature ids are processed.
The \fIfeature ID\fR is an internal (unique) geometry ID that all vector
primitives possess, and is separate from any category the feature may
also possess.
Use
.br
.nf
\fC
  \fIv.edit\fR map=inputname tool=select
\fR
.fi
to find out the geometry ids of certain features.
.SH EXAMPLES
.SS Report vector categories
.br
.nf
\fC
v.category input=testmap option=report
LAYER/TABLE 1/testmap:
type       count        min        max
point          0          0          0
line        1379          1       1379
boundary       0          0          0
centroid       0          0          0
area           0          0          0
all         1379          1       1379
\fR
.fi
.SS Delete all vector categories in layer 1
.br
.nf
\fC
v.category input=testmap output=outmap option=del cat=\-1
\fR
.fi
.SS Add vector categories in layer 1 with step=2
.br
.nf
\fC
v.category input=outmap output=stepmap option=add step=2
# report
v.category input=stepmap option=report
LAYER/TABLE 1/outmap:
type       count        min        max
point          0          0          0
line        1379          1       2757
boundary       0          0          0
centroid       0          0          0
area           0          0          0
all         1379          1       2757
\fR
.fi
.SS Add categories/centroids to a vector map without categories
.br
.nf
\fC
v.category input=wkt output=wktnew option=add
\fR
.fi
Results can be tested
using \fId.what.vect\fR.
.SS Copy categories from layer 1 to layer 2,3,4,5,6,7 and 8
Existing layer will be overwritten, non\-existing will be created.
.br
.nf
\fC
v.category input=observer output=observer_new option=transfer layer=1,2,3,4,5,6,7,8
\fR
.fi
.SS Print vector categories of given layer
Print vector categories from the first layer, only for feature ids 1\-50.
.br
.nf
\fC
v.category input=roads option=print layer=1 id=1\-50
\fR
.fi
.SH SEE ALSO
\fI
v.centroids,
v.db.connect,
v.edit,
v.to.db
\fR
.SH AUTHOR
Radim Blazek, ITC\-irst, Trento, Italy
.br
Modified (the id parameter) by Martin Landa,
FBK\-irst (formerly ITC\-irst), Trento, Italy, 2008/02
.SH SOURCE CODE
.PP
Available at: v.category source code (history)
.PP
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.PP
© 2003\-2020
GRASS Development Team,
GRASS GIS 7.8.5 Reference Manual