# strength: Strength or weighted vertex degree

## Description

Summing up the edge weights of the adjacent edges for each vertex.

## Usage

strength(
graph,
vids = V(graph),
mode = c("all", "out", "in", "total"),
loops = TRUE,
weights = NULL
)

## Arguments

vids

The vertices for which the strength will be calculated.

mode

Character string, “out” for out-degree, “in” for
in-degree or “all” for the sum of the two. For undirected graphs this
argument is ignored.

loops

Logical; whether the loop edges are also counted.

weights

Weight vector. If the graph has a `weight`

edge
attribute, then this is used by default. If the graph does not have a
`weight`

edge attribute and this argument is `NULL`

, then a
warning is given and `degree`

is called.

## Value

A numeric vector giving the strength of the vertices.

## References

Alain Barrat, Marc Barthelemy, Romualdo Pastor-Satorras,
Alessandro Vespignani: The architecture of complex weighted networks, Proc.
Natl. Acad. Sci. USA 101, 3747 (2004)

## See Also

`degree`

for the unweighted version.

## Examples

# NOT RUN {
g <- make_star(10)
E(g)$weight <- seq(ecount(g))
strength(g)
strength(g, mode="out")
strength(g, mode="in")
# No weights, a warning is given
g <- make_ring(10)
strength(g)
# }