Finds blocks of nodes with intra-positive and inter-negative edges

signed_blockmodel(g, k, alpha = 0.5, annealing = FALSE)

## Arguments

g

igraph object with a sign edge attribute.

k

number of blocks

alpha

see details

annealing

logical. if TRUE, use simulated annealing (Default: FALSE)

## Value

numeric vector of block assignments and the associated criterion value

## Details

The function minimizes P(C)=$$\alpha$$N+(1-$$\alpha$$)P, where N is the total number of negative ties within plus-sets and P be the total number of positive ties between plus-sets. This function implementes the structural balance model. That is, all diagonal blocks are positive and off-diagonal blocks negative. For the generalized version see signed_blockmodel_general.

## References

Doreian, Patrick and Andrej Mrvar (2009). Partitioning signed social networks. Social Networks 31(1) 1-11

David Schoch

## Examples

library(igraph)

g <- sample_islands_signed(10, 10, 1, 20)
clu <- signed_blockmodel(g, k = 10, alpha = 0.5)
table(clu$membership) #> #> 1 2 3 4 5 6 7 8 9 10 #> 10 10 10 10 10 10 10 10 10 10 clu$criterion
#> [1] 0

# Using simulated annealing (less change of getting trapped in local optima)
data("tribes")
clu <- signed_blockmodel(tribes, k = 3, alpha = 0.5, annealing = TRUE)
table(clu$membership) #> #> 1 2 3 #> 4 7 5 clu$criterion
#> [1] 2