1v.net.flow(1) GRASS GIS User's Manual v.net.flow(1)
2
6 v.net.flow - Computes the maximum flow between two sets of nodes in
7 the network.
8
10 vector, network, flow
11
13 v.net.flow
14 v.net.flow --help
15 v.net.flow input=name [arc_layer=string] [node_layer=string] out‐
16 put=name cut=name [arc_column=name] [arc_backward_column=name]
17 [node_column=name] [source_cats=range] [source_where=sql_query]
18 [sink_cats=range] [sink_where=sql_query] [--overwrite] [--help]
19 [--verbose] [--quiet] [--ui]
20 Flags:
22 --overwrite
23 Allow output files to overwrite existing files
24 --help
26 Print usage summary
27 --verbose
29 Verbose module output
30 --quiet
32 Quiet module output
33 --ui
35 Force launching GUI dialog
36 Parameters:
38 input=name [required]
39 Name of input vector map
40 Or data source for direct OGR access
41 arc_layer=string
43 Arc layer
44 Vector features can have category values in different layers. This
45 number determines which layer to use. When used with direct OGR
46 access this is the layer name.
47 Default: 1
48 node_layer=string
50 Node layer
51 Vector features can have category values in different layers. This
52 number determines which layer to use. When used with direct OGR
53 access this is the layer name.
54 Default: 2
55 output=name [required]
57 Name for output vector map
58 cut=name [required]
60 Name for output vector map containing a minimum cut
61 arc_column=name
63 Arc forward/both direction(s) cost column (number)
64 arc_backward_column=name
66 Arc backward direction cost column (number)
67 node_column=name
69 Node cost column (number)
70 source_cats=range
72 Source category values
73 Example: 1,3,7-9,13
74 source_where=sql_query
76 Source WHERE conditions of SQL statement without ’where’ keyword
77 Example: income < 1000 and population >= 10000
78 sink_cats=range
80 Sink category values
81 Example: 1,3,7-9,13
82 sink_where=sql_query
84 Sink WHERE conditions of SQL statement without ’where’ keyword
85 Example: income < 1000 and population >= 10000
86
88 v.net.flow computes the maximum flow and minimum cut between two sets
89 of nodes.
90
92 The two sets of nodes are called sources and sink and v.net.flow finds
93 the maximum flow from the former to the latter ones. Edge capacities
94 can be specified by arc_column for forward direction and arc_back‐
95 ward_column for backward direction. If the latter parameter is omitted
96 then the same capacity is used in either direction. The sets are given
97 by the respective cats, layer and where parameters. Maximum flow corre‐
98 sponds to the maximum amount of water possibly flowing through the net‐
99 work preserving the capacity constraints and minimum cut to the set of
100 edges of minimum total capacity completely separating sources from
101 sinks. The cut produced by this module corresponds to the first fully
102 saturated edges from sources to sinks. An attribute table containing
103 the flow information is linked to the output map. The table consists of
104 two columns: cat and flow and stores the flow along each line. Negative
105 flow means that "water" is flowing in the backward direction. Cut map
106 contains the edges in the minimum cut.
107 A famous result says that the total amount of water flowing is equal to
108 the minimum cut.
109
111 Find maximum flow from factories to stores using SPEED for the capaci‐
112 ties.
113 v.net.flow input=roads output=roads_flow cut=roads_cut arc_column=SPEED \
114 source_where="type=factory" sink_where="type=store"
115 If all the capacties are one then the minimum cut corresponds to the
117 minimum number of edges separating sources from sinks.
118 v.net.flow input=network output=flow cut=cut arc_column=ones \
119 source_cats=1-10 sink_cats=100-100
120
122 v.net, v.net.connectivity
123
125 Daniel Bundala, Google Summer of Code 2009, Student
126 Wolf Bergenheim, Mentor
127
129 Available at: v.net.flow source code (history)
130 Main index | Vector index | Topics index | Keywords index | Graphical
132 index | Full index
133 © 2003-2020 GRASS Development Team, GRASS GIS 7.8.5 Reference Manual
135GRASS 7.8.5 v.net.flow(1)