.TH v.net.centrality 1grass "" "GRASS 6.4.4" "Grass User's Manual"
.SH NAME
\fI\fBv.net.centrality\fR\fR  - Computes degree, centrality, betweeness, closeness and eigenvector centrality measures in the network.
.SH KEYWORDS
vector, network, centrality measures
.SH SYNOPSIS
\fBv.net.centrality\fR
.br
\fBv.net.centrality help\fR
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\fBv.net.centrality\fR [\-\fBga\fR] \fBinput\fR=\fIname\fR  [\fBlayer\fR=\fIinteger\fR]  \fBoutput\fR=\fIname\fR  [\fBcats\fR=\fIrange\fR]   [\fBwhere\fR=\fIsql_query\fR]   [\fBafcolumn\fR=\fIname\fR]   [\fBabcolumn\fR=\fIname\fR]   [\fBdegree\fR=\fIname\fR]   [\fBcloseness\fR=\fIname\fR]   [\fBbetweenness\fR=\fIname\fR]   [\fBeigenvector\fR=\fIname\fR]   [\fBiterations\fR=\fIinteger\fR]   [\fBerror\fR=\fIfloat\fR]   [\-\-\fBoverwrite\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR] 
.SS Flags:
.IP "\fB\-g\fR" 4m
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Use geodesic calculation for longitude-latitude locations
.IP "\fB\-a\fR" 4m
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Add points on nodes
.IP "\fB\-\-overwrite\fR" 4m
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Allow output files to overwrite existing files
.IP "\fB\-\-verbose\fR" 4m
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Verbose module output
.IP "\fB\-\-quiet\fR" 4m
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Quiet module output
.PP
.SS Parameters:
.IP "\fBinput\fR=\fIname\fR" 4m
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Name of input vector map
.IP "\fBlayer\fR=\fIinteger\fR" 4m
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Layer number
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A single vector map can be connected to multiple database tables. This number determines which table to use.
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Default: \fI1\fR
.IP "\fBoutput\fR=\fIname\fR" 4m
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Name for output vector map
.IP "\fBcats\fR=\fIrange\fR" 4m
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Category values
.br
Example: 1,3,7-9,13
.IP "\fBwhere\fR=\fIsql_query\fR" 4m
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WHERE conditions of SQL statement without 'where' keyword
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Example: income = 10000
.IP "\fBafcolumn\fR=\fIname\fR" 4m
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Name of arc forward/both direction(s) cost column
.IP "\fBabcolumn\fR=\fIname\fR" 4m
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Name of arc backward direction cost column
.IP "\fBdegree\fR=\fIname\fR" 4m
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Name of degree centrality column
.IP "\fBcloseness\fR=\fIname\fR" 4m
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Name of closeness centrality column
.IP "\fBbetweenness\fR=\fIname\fR" 4m
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Name of betweenness centrality column
.IP "\fBeigenvector\fR=\fIname\fR" 4m
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Name of eigenvector centrality column
.IP "\fBiterations\fR=\fIinteger\fR" 4m
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Maximum number of iterations to compute eigenvector centrality
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Default: \fI1000\fR
.IP "\fBerror\fR=\fIfloat\fR" 4m
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Cummulative error tolerance for eigenvector centrality
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Default: \fI0.1\fR
.PP
.SH DESCRIPTION
\fIv.net.centrality\fR computes degree, closeness, betweenness 
and eigenvector centrality measures. 
.SH NOTES
The module computes various centrality measures for each node and 
stores them in the given columns of an attribute table, which is 
created and linked to the output map. For the description of these, 
please check the following
wikipedia article.
If the column name is not given for a measure then that measure is not 
computed. If \fB-a\fR flag is set then points are added on nodes 
without points. Also, the points for which the output is computed 
can be specified by \fBcats\fR, \fBlayer\fR and \fBwhere\fR 
parameters. However, if any of these parameters is present then
\fB-a\fR flag is ignored and no new points are added.
.br
Betweenness measure is not normalised. In order to get the normalised 
values (between 0 and 1), each number needs to be divided by \fIN 
choose 2=N*(N-1)/2\fR where N is the number of nodes in the 
connected component. Computation of eigenvector measure terminates 
if the given number of iterations is reached or the cummulative \fI
squared\fR error between the successive iterations is less than \fB
error\fR.
.SH EXAMPLES
Compute closeness and betweenness centrality measures for each node 
and produce a map containing not only points already present in the 
input map but a map with point on every node.
\fC
.DS
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v.net.centrality input=roads output=roads_cent closeness=closeness \(rs
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      betweenness=betweenness \-a
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.DE
\fR
.SH SEE ALSO
\fI
v.net,
v.generalize
\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
Full index
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© 2003-2014 GRASS Development Team