# Shortest (directed or undirected) paths between vertices

Source:`R/structural.properties.R`

`get.shortest.paths.Rd`

`get.shortest.paths()`

was renamed to `shortest_paths()`

to create a more
consistent API.

## Arguments

- graph
The graph to work on.

- 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, the vertices to which the shortest paths will be calculated. By default it includes all vertices. Note that for

`distances()`

every vertex must be included here at most once. (This is not required for`shortest_paths()`

.- 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 graph is treated as undirected, i.e. edge directions are not taken into account. This argument is ignored for undirected graphs.- weights
Possibly a numeric vector giving edge weights. If this is

`NULL`

and the graph has a`weight`

edge attribute, then the attribute is used. If this is`NA`

then no weights are used (even if the graph has a`weight`

attribute). In a weighted graph, the length of a path is the sum of the weights of its constituent edges.- output
Character scalar, defines how to report the shortest paths. “vpath” means that the vertices along the paths are reported, this form was used prior to igraph version 0.6. “epath” means that the edges along the paths are reported. “both” means that both forms are returned, in a named list with components “vpath” and “epath”.

- predecessors
Logical scalar, whether to return the predecessor vertex for each vertex. The predecessor of vertex

`i`

in the tree is the vertex from which vertex`i`

was reached. The predecessor of the start vertex (in the`from`

argument) is itself by definition. If the predecessor is zero, it means that the given vertex was not reached from the source during the search. Note that the search terminates if all the vertices in`to`

are reached.- inbound.edges
Logical scalar, whether to return the inbound edge for each vertex. The inbound edge of vertex

`i`

in the tree is the edge via which vertex`i`

was reached. The start vertex and vertices that were not reached during the search will have zero in the corresponding entry of the vector. Note that the search terminates if all the vertices in`to`

are reached.- algorithm
Which algorithm to use for the calculation. By default igraph tries to select the fastest suitable algorithm. If there are no weights, then an unweighted breadth-first search is used, otherwise if all weights are positive, then Dijkstra's algorithm is used. If there are negative weights and we do the calculation for more than 100 sources, then Johnson's algorithm is used. Otherwise the Bellman-Ford algorithm is used. You can override igraph's choice by explicitly giving this parameter. Note that the igraph C core might still override your choice in obvious cases, i.e. if there are no edge weights, then the unweighted algorithm will be used, regardless of this argument.