.TH v.net.flow 1grass "" "GRASS 8.3.1" "GRASS GIS User's Manual"
.SH NAME
\fI\fBv.net.flow\fR\fR  \- Computes the maximum flow between two sets of nodes in the network.
.SH KEYWORDS
vector, network, flow
.SH SYNOPSIS
\fBv.net.flow\fR
.br
\fBv.net.flow \-\-help\fR
.br
\fBv.net.flow\fR \fBinput\fR=\fIname\fR  [\fBarc_layer\fR=\fIstring\fR]   [\fBnode_layer\fR=\fIstring\fR]  \fBoutput\fR=\fIname\fR \fBcut\fR=\fIname\fR  [\fBarc_column\fR=\fIname\fR]   [\fBarc_backward_column\fR=\fIname\fR]   [\fBnode_column\fR=\fIname\fR]   [\fBsource_cats\fR=\fIrange\fR]   [\fBsource_where\fR=\fIsql_query\fR]   [\fBsink_cats\fR=\fIrange\fR]   [\fBsink_where\fR=\fIsql_query\fR]   [\-\-\fBoverwrite\fR]  [\-\-\fBhelp\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR]  [\-\-\fBui\fR]
.SS Flags:
.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 "\fBarc_layer\fR=\fIstring\fR" 4m
.br
Arc layer
.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 "\fBnode_layer\fR=\fIstring\fR" 4m
.br
Node layer
.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: \fI2\fR
.IP "\fBoutput\fR=\fIname\fR \fB[required]\fR" 4m
.br
Name for output vector map
.IP "\fBcut\fR=\fIname\fR \fB[required]\fR" 4m
.br
Name for output vector map containing a minimum cut
.IP "\fBarc_column\fR=\fIname\fR" 4m
.br
Arc forward/both direction(s) cost column (number)
.IP "\fBarc_backward_column\fR=\fIname\fR" 4m
.br
Arc backward direction cost column (number)
.IP "\fBnode_column\fR=\fIname\fR" 4m
.br
Node cost column (number)
.IP "\fBsource_cats\fR=\fIrange\fR" 4m
.br
Source category values
.br
Example: 1,3,7\-9,13
.IP "\fBsource_where\fR=\fIsql_query\fR" 4m
.br
Source WHERE conditions of SQL statement without \(cqwhere\(cq keyword
.br
Example: income < 1000 and population >= 10000
.IP "\fBsink_cats\fR=\fIrange\fR" 4m
.br
Sink category values
.br
Example: 1,3,7\-9,13
.IP "\fBsink_where\fR=\fIsql_query\fR" 4m
.br
Sink WHERE conditions of SQL statement without \(cqwhere\(cq keyword
.br
Example: income < 1000 and population >= 10000
.SH DESCRIPTION
\fIv.net.flow\fR computes the maximum flow and minimum cut
between two sets of nodes.
.SH NOTES
The two sets of nodes are called \fIsources\fR and \fIsink\fR
and \fIv.net.flow\fR finds the maximum flow from the former to
the latter ones. Edge capacities can be specified by \fBarc_column\fR
for forward direction and \fBarc_backward_column\fR for backward direction. If
the latter parameter is omitted then the same capacity is used in
either direction. The sets are given by the respective \fBcats\fR,
\fBlayer\fR and \fBwhere\fR parameters. Maximum flow corresponds
to the maximum amount of water possibly flowing through the network
preserving the capacity constraints and minimum cut to the set of edges
of minimum total capacity completely separating sources from sinks.
The cut produced by this module corresponds to the first fully
saturated edges from sources to sinks. An attribute table containing
the flow information is linked to the \fBoutput\fR map. The table
consists of two columns: \fIcat\fR and \fIflow\fR and stores
the flow along each line. Negative flow means that \(dqwater\(dq is
flowing in the backward direction. \fBCut\fR map contains the edges
in the minimum cut.
.br
A famous result
says that the total amount of water flowing is equal to the minimum
cut.
.SH EXAMPLES
Find maximum flow from factories to stores using SPEED for the capacities.
.br
.nf
\fC
v.net.flow input=roads output=roads_flow cut=roads_cut arc_column=SPEED \(rs
           source_where=\(dqtype=factory\(dq sink_where=\(dqtype=store\(dq
\fR
.fi
.PP
If all the capacties are one then the minimum cut corresponds to the
minimum number of edges separating sources from sinks.
.br
.nf
\fC
v.net.flow input=network output=flow cut=cut arc_column=ones \(rs
           source_cats=1\-10 sink_cats=100\-100
\fR
.fi
.SH SEE ALSO
\fI
v.net,
v.net.connectivity
\fR
.SH AUTHORS
Daniel Bundala, Google Summer of Code 2009, Student
.br
Wolf Bergenheim, Mentor
.SH SOURCE CODE
.PP
Available at:
v.net.flow source code
(history)
.PP
Accessed: Sunday Dec 17 17:22:25 2023
.PP
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.PP
© 2003\-2023
GRASS Development Team,
GRASS GIS 8.3.1 Reference Manual