.TH v.net.components 1grass "" "GRASS 6.4.4" "Grass User's Manual"
.SH NAME
\fI\fBv.net.components\fR\fR  - Computes strongly and weakly connected components in the network.
.SH KEYWORDS
vector, network, components
.SH SYNOPSIS
\fBv.net.components\fR
.br
\fBv.net.components help\fR
.br
\fBv.net.components\fR [\-\fBa\fR] \fBinput\fR=\fIname\fR  [\fBlayer\fR=\fIinteger\fR]  \fBoutput\fR=\fIname\fR \fBmethod\fR=\fIstring\fR  [\-\-\fBoverwrite\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR] 
.SS Flags:
.IP "\fB\-a\fR" 4m
.br
Add points on nodes
.IP "\fB\-\-overwrite\fR" 4m
.br
Allow output files to overwrite existing files
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.PP
.SS Parameters:
.IP "\fBinput\fR=\fIname\fR" 4m
.br
Name of input vector map
.IP "\fBlayer\fR=\fIinteger\fR" 4m
.br
Layer number
.br
A single vector map can be connected to multiple database tables. This number determines which table to use.
.br
Default: \fI1\fR
.IP "\fBoutput\fR=\fIname\fR" 4m
.br
Name for output vector map
.IP "\fBmethod\fR=\fIstring\fR" 4m
.br
Type of components
.br
Options: \fIweak,strong\fR
.br
\fBweak\fR: Weakly connected components
.br
\fBstrong\fR: Strongly connected components
.PP
.SH DESCRIPTION
\fIv.net.components\fR computes the weakly and strongly connected 
components in a network.
.SH NOTES
Two nodes, \fIu\fR and \fIv\fR are in the same strongly 
connected component if there are directed paths from \fIu\fR to 
\fIv\fR and from \fIv\fR to \fIu\fR. The nodes are in the 
same weakly connected component if, ignoring orientation of the 
edges, there is a path between them.
.br
The type of components is specified by \fBmethod\fR parameter. 
\fIv.net.components\fR creates a table and links it to the given \fBlayer\fR.
This table contains only two integer columns: \fIcat\fR and \fIcomp
\fR. If a point or both endpoints of a line belong to the same 
component then the point/line is written to the output map and 
appropriate information is stored in the table. If \fB-a\fR flag is 
set then new points are added on the nodes without points. These 
points have category numbers larger than any category used in the 
input map.
.SH EXAMPLES
Any road network should form a single strongly connected component. 
Otherwise, it is impossible to travel between some places.
\fC
.DS
.br
v.net.components input=roads output=roads_components method=strong
.br
.DE
\fR
.SH SEE ALSO
\fI
v.net,
v.category,
\fR
.SH AUTHORS
Daniel Bundala, Google Summer of Code 2009, Student
.br
Wolf Bergenheim, Mentor
.PP
\fILast changed: $Date: 2013-05-23 22:01:55 +0200 (Thu, 23 May 2013) $\fR
.PP
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.PP
© 2003-2014 GRASS Development Team