Finds blocks of nodes with intra-positive and inter-negative edges
signed_blockmodel(g, k, alpha = 0.5, annealing = FALSE)igraph object with a sign edge attribute.
number of blocks
see details
logical. if TRUE, use simulated annealing (Default: FALSE)
numeric vector of block assignments and the associated criterion value
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 implements the structural balance model. That is, all diagonal blocks are positive and off-diagonal blocks negative. For the generalized version see signed_blockmodel_general.
Doreian, Patrick and Andrej Mrvar (2009). Partitioning signed social networks. Social Networks 31(1) 1-11
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$membership)
#>
#> 1 2 3
#> 7 4 5
clu$criterion
#> [1] 2