Scale-free networks grown via preferential attachment have been used to model real-world networks such as the Internet, citation networks, and social networks. Here we investigate signed scale-free networks where a link represents a positive or negative connection. We present analytic results and simulations for a growing signed network model and compare the signed network to an unsigned scale-free network. We discuss several options for preferential attachment in a signed network model. Lastly we measure preferential attachment in a real-world network and discuss the advantages and disadvantages of data fitting methods
