In weighted graphs, a real number is assigned to each (directed or undirected) edge.
Details
In igraph edge weights are represented via an edge attribute, called
‘weight’. The is_weighted() function only checks that such an
attribute exists. (It does not even checks that it is a numeric edge
attribute.)
Edge weights are used for different purposes by the different functions. E.g. shortest path functions use it as the cost of the path; community finding methods use it as the strength of the relationship between two vertices, etc. Check the manual pages of the functions working with weighted graphs for details.
Author
Gabor Csardi csardi.gabor@gmail.com
Examples
g <- make_ring(10)
shortest_paths(g, 8, 2)
#> $vpath
#> $vpath[[1]]
#> + 5/10 vertices, from b159add:
#> [1] 8 9 10 1 2
#>
#>
#> $epath
#> NULL
#>
#> $predecessors
#> NULL
#>
#> $inbound_edges
#> NULL
#>
E(g)$weight <- seq_len(ecount(g))
shortest_paths(g, 8, 2)
#> $vpath
#> $vpath[[1]]
#> + 7/10 vertices, from b159add:
#> [1] 8 7 6 5 4 3 2
#>
#>
#> $epath
#> NULL
#>
#> $predecessors
#> NULL
#>
#> $inbound_edges
#> NULL
#>