arranges nodes in concentric circles according to a centrality index.

## Arguments

- g
igraph object

- cent
centrality scores

- scale
logical. should centrality scores be scaled to \([0,100]\)? (Default: TRUE)

- iter
number of iterations during stress optimization

- tol
stopping criterion for stress optimization

- tseq
numeric vector. increasing sequence of coefficients to combine regular stress and constraint stress. See details.

- circular
not used

## Details

The function optimizes a convex combination of regular stress and a constrained stress function which forces
nodes to be arranged on concentric circles. The vector `tseq`

is the sequence of parameters used for the convex combination.
In iteration i of the algorithm \(tseq[i]\) is used to combine regular and constraint stress as \((1-tseq[i])*stress_{regular}+tseq[i]*stress_{constraint}\). The sequence must be increasing, start at zero and end at one. The default setting should be a good choice for most graphs.

The layout_igraph_* function should not be used directly. It is only used as an argument for plotting with 'igraph'. 'ggraph' natively supports the layout.

## References

Brandes, U., & Pich, C. (2011). More flexible radial layout. Journal of Graph Algorithms and Applications, 15(1), 157-173.

## Examples

```
library(igraph)
library(ggraph)
g <- sample_gnp(10, 0.4)
if (FALSE) {
ggraph(g, layout = "centrality", centrality = closeness(g)) +
draw_circle(use = "cent") +
geom_edge_link0() +
geom_node_point(shape = 21, fill = "grey25", size = 5) +
theme_graph() +
coord_fixed()
}
```