# strength

##### Strength or weighted vertex degree

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

- Keywords
- graphs

##### Usage

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

##### Arguments

- graph
The input graph.

- 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)
# }
```

*Documentation reproduced from package igraph, version 1.0.1, License: GPL (>= 2)*