shortest.paths {igraph} | R Documentation |
shortest.paths
calculates the length of all the
shortest paths from or to the vertices in the
network. get.shortest.paths
calculates one shortest path (the
path itself, and not just its length) from or to the given vertex.
shortest.paths(graph, v=V(graph), mode = "all") get.shortest.paths(graph, from, to=V(graph), mode = "all") get.all.shortest.paths(graph, from, to = V(graph), mode = "all") average.path.length(graph, directed=TRUE, unconnected=TRUE)
graph |
The graph to work on. |
v |
Numeric vector, the vertices from or to which the shortest paths will be calculated. |
mode |
Character constant, gives whether the shortest paths to or
from the given vertices should be calculated for directed graphs. If
out then the shortest paths from the vertex, if
in then to it will be considered. If all , the
default, then the corresponding undirected graph will be used,
ie. not directed paths are searched. This argument is ignored for
undirected graphs. |
from |
Numeric constant, the vertex from or to the shortest paths will be calculated. Note that right now this is not a vector of vertex ids, but only a single vertex. |
to |
Numeric vector, only the shortest paths to these vertices will be calculated. Defaults to all vertices. |
directed |
Whether to consider directed paths in directed graphs, this argument is ignored for undirected graphs. |
unconnected |
What to do if the graph is unconnected (not
strongly connected if directed paths are considered). If TRUE only
the lengths of the existing paths are considered and averaged; if
FALSE the length of the missing paths are counted having length
vcount(graph) , one longer than the longest possible geodesic
in the network. |
The shortest paths (also called geodesics) are calculated by using breath-first search in the graph. Right now edge weights are not used, ie. every edge weight is one.
Note that shortest.paths
is able to calculate the path length
from or to many vertices at the same time, but
get.shortest.paths
works from one source only. This might
change in the future.
Also note that get.shortest.paths
gives only one shortest path,
however more than one might exists between two vertices.
get.all.shortest.paths
calculates all shortest paths from a
vertex to other vertices given in the to
argument.
For shortest.paths
a numeric matrix with vcount(graph)
columns and length(v)
rows. The shortest path length from a vertex to
itself is always zero.
For get.shortest.paths
a list of length
vcount(graph)
. List element i
contains the vertex ids on
the path from vertex from
to vertex i
(or the other way
for directed graphs depending on the mode
argument). The vector
also contains from
and i
as the first and last
elements. If from
is the same as i
then it is only
included once. If there is no path between two vertices then a
numeric vector of length zero is returned as the list element.
For get.all.shortest.paths
a list is returned, each list
element contains a shortest path from from
to a vertex in
to
. The shortest paths to the same vertex are collected into
consecutive elements of the list.
For average.path.length
a single number is returned.
Gabor Csardi csardi@rmki.kfki.hu
West, D.B. (1996). Introduction to Graph Theory. Upper Saddle River, N.J.: Prentice Hall.
g <- graph.ring(10) shortest.paths(g) get.shortest.paths(g, 5) get.all.shortest.paths(g, 0, 5:7) average.path.length(g)