Note: This document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade, and read the current manual page.
NAME
v.net.flow  - Computes the maximum flow between two sets of nodes in the network.
KEYWORDS
vector, 
network, 
flow
SYNOPSIS
v.net.flow
v.net.flow --help
v.net.flow input=name  [arc_layer=string]   [node_layer=string]  output=name cut=name  [arc_column=name]   [arc_backward_column=name]   [node_column=name]   [source_cats=range]   [source_where=sql_query]   [sink_cats=range]   [sink_where=sql_query]   [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui] 
Flags:
- --overwrite
 
- Allow output files to overwrite existing files
 
- --help
 
- Print usage summary
 
- --verbose
 
- Verbose module output
 
- --quiet
 
- Quiet module output
 
- --ui
 
- Force launching GUI dialog
 
 
Parameters:
- input=name [required]
 
- Name of input vector map
 
- Or data source for direct OGR access
 
- arc_layer=string
 
- Arc layer
 
- 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.
 
- Default: 1
 
- node_layer=string
 
- Node layer
 
- 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.
 
- Default: 2
 
- output=name [required]
 
- Name for output vector map
 
- cut=name [required]
 
- Name for output vector map containing a minimum cut
 
- arc_column=name
 
- Arc forward/both direction(s) cost column (number)
 
- arc_backward_column=name
 
- Arc backward direction cost column (number)
 
- node_column=name
 
- Node cost column (number)
 
- source_cats=range
 
- Source category values
 
- Example: 1,3,7-9,13
 
- source_where=sql_query
 
- Source WHERE conditions of SQL statement without 'where' keyword
 
- Example: income < 1000 and population >= 10000
 
- sink_cats=range
 
- Sink category values
 
- Example: 1,3,7-9,13
 
- sink_where=sql_query
 
- Sink WHERE conditions of SQL statement without 'where' keyword
 
- Example: income < 1000 and population >= 10000
 
 
v.net.flow computes the maximum flow and minimum cut 
between two sets of nodes.
The two sets of nodes are called 
sources and 
sink 
and 
v.net.flow finds the maximum flow from the former to 
the latter ones. Edge capacities can be specified by 
arc_column 
for forward direction and 
arc_backward_column 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 
cats, 
layer and 
where 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 
output map. The table 
consists of two columns: 
cat and 
flow and stores 
the flow along each line. Negative flow means that "water" is 
flowing in the backward direction. 
Cut map contains the edges 
in the minimum cut.
A famous 
result 
says that the total amount of water flowing is equal to the minimum 
cut.
Find maximum flow from factories to stores using SPEED for the capacities.
v.net.flow input=roads output=roads_flow cut=roads_cut arc_column=SPEED \
           source_where="type=factory" sink_where="type=store"
 
If all the capacties are one then the minimum cut corresponds to the 
minimum number of edges separating sources from sinks. 
v.net.flow input=network output=flow cut=cut arc_column=ones \
           source_cats=1-10 sink_cats=100-100
 
v.net,
v.net.connectivity
Daniel Bundala, Google Summer of Code 2009, Student
Wolf Bergenheim, Mentor
SOURCE CODE
  Available at:
  v.net.flow source code
  (history)
  Latest change: Thursday Feb 03 11:10:06 2022 in commit: 547ff44e6aecfb4c9cbf6a4717fc14e521bec0be
Note: This document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade, and read the current manual page.
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GRASS Development Team,
GRASS GIS 8.2.2dev Reference Manual