# evcent

##### Find Eigenvector Centrality Scores of Network Positions

`evcent`

takes a graph (`graph`

) and returns the
eigenvector centralities of positions `v`

within it

- Keywords
- graphs

##### Usage

```
evcent (graph, directed = FALSE, scale = TRUE, weights = NULL,
options = igraph.arpack.default)
```

##### Arguments

- graph
- Graph to be analyzed.
- directed
- Logical scalar, whether to consider direction of the edges in directed graphs. It is ignored for undirected graphs.
- scale
- Logical scalar, whether to scale the result to have a maximum score of one. If no scaling is used then the result vector has unit length in the Euclidean norm.
- weights
- A numerical vector or
`NULL`

. This argument can be used to give edge weights for calculating the weighted eigenvector centrality of vertices. If this is`NULL`

and the graph has a`weight`

edge attribute then t - options
- A named list, to override some ARPACK options. See
`arpack`

for details.

##### Details

Eigenvector centrality scores correspond to the values of the first eigenvector of the graph adjacency matrix; these scores may, in turn, be interpreted as arising from a reciprocal process in which the centrality of each actor is proportional to the sum of the centralities of those actors to whom he or she is connected. In general, vertices with high eigenvector centralities are those which are connected to many other vertices which are, in turn, connected to many others (and so on). (The perceptive may realize that this implies that the largest values will be obtained by individuals in large cliques (or high-density substructures). This is also intelligible from an algebraic point of view, with the first eigenvector being closely related to the best rank-1 approximation of the adjacency matrix (a relationship which is easy to see in the special case of a diagonalizable symmetric real matrix via the $SLS^-1$ decomposition).)

From igraph version 0.5 this function uses ARPACK for the underlying
computation, see `arpack`

for more about ARPACK in igraph.

##### Value

- A named list with components:
vector A vector containing the centrality scores. value The eigenvalue corresponding to the calculated eigenvector, i.e. the centrality scores. options A named list, information about the underlying ARPACK computation. See `arpack`

for the details.

##### concept

Eigenvector centrality

##### WARNING

`evcent`

will not symmetrize your data before
extracting eigenvectors; don't send this routine asymmetric matrices
unless you really mean to do so.

##### References

Bonacich, P. (1987). Power and Centrality: A Family of
Measures. *American Journal of Sociology*, 92, 1170-1182.

##### Examples

```
#Generate some test data
g <- graph.ring(10, directed=FALSE)
#Compute eigenvector centrality scores
evcent(g)
```

*Documentation reproduced from package igraph, version 0.6.5-2, License: GPL (>= 2)*