By Yunkyu Sohn
Below are the two papers recently published in PRE. They generalized modularity parameter for networks with positive and negative links. Especially Traag and Bruggeman analyzed Correlates of War data by assigning alliance relationship as positive weight and the presence of dispute as negative weight. Modularity optimization method used for each study is linked below.
Analysis of community structure in networks of correlated data S. Gómez, P. Jensen and A. Arenas, Physical Review E 80, 016114 (2009)
optimization method used: http://arxiv.org/abs/physics/0703218
Community detection in networks with positive and negative links V. A. Traag and Jeroen Bruggeman, Physical Review E 80, 036115 (2009)
optimization method used: http://www.itp.uni-bremen.de/complex/pre016110.pdf
Traag and Bruggeman’s parameter will be implemented in igraph 0.6.