.TH v.net.allpairs 1grass "" "GRASS 6.4.2" "Grass User's Manual"
.SH NAME
\fI\fBv.net.allpairs\fR\fR  - Computes the shortest path between all pairs of nodes in the network.
.SH KEYWORDS
vector, network, shortest path
.SH SYNOPSIS
\fBv.net.allpairs\fR
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\fBv.net.allpairs help\fR
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\fBv.net.allpairs\fR [-\fBga\fR] \fBinput\fR=\fIname\fR \fBoutput\fR=\fIname\fR  [\fBlayer\fR=\fIinteger\fR]   [\fBcats\fR=\fIrange\fR]   [\fBwhere\fR=\fIsql_query\fR]   [\fBafcolumn\fR=\fIname\fR]   [\fBabcolumn\fR=\fIname\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 without points
.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 "\fBoutput\fR=\fIname\fR" 4m
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Name for output 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 "\fBcats\fR=\fIrange\fR" 4m
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Category values
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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
.PP
.SH DESCRIPTION
\fIv.net.allpairs\fR computes the shortest path between each select node and all other nodes. 
.SH NOTES
An attribute table is created and linked to \fBlayer\fR. The table contains three columns: \fIcat\fR, \fIto_cat\fR, \fIcost\fR. Each entry denotes the cost of the shortest path from \fIcat\fR to \fIto_cat\fR. If the cost is negative then no path exists. If points are specified by \fBcats, layer\fR or \fBwhere\fR parameters then the table is filled only for the selected points. In other words, \fIcat\fR columns contains only selected points but the distances are computed and updated for \fIall\fR other nodes.
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If flag \fB-a\fR is set then new points are added on nodes without nodes. These points have the largest categorie. Precisely, category of each new point is larger than any of the old categories. If the flag is not set then no new points are created and hence the attribute table stores the costs only between the points already present in the input. Output consists of all points mentioned in either of the columns.
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If \fBabcolumn\fR is not given then then the same costs are used for forward and backward arcs.
.SH EXAMPLES
Find shortest path from each intersection with pedestrian crossing to every other point using \fISHAPE_LEN\fR for the cost of traversing the arcs in both directions.
\fC
.DS
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v.net.allpairs input=roads output=roads_pairs afcol=SHAPE_LEN where="crossing=1"
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.DE
\fR
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.SH SEE ALSO
\fI
v.net.path,
v.net.distance
\fR
.SH AUTHORS
Daniel Bundala, Google Summer of Code 2009, Student
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Wolf Bergenheim, Mentor
.PP
\fILast changed: $Date: 2011-11-08 10:42:51 +0100 (Tue, 08 Nov 2011) $\fR
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Full index
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© 2003-2011 GRASS Development Team