  We study mixing patterns in networks, meaning the propensity for nodes of
different kinds to connect to one another. The phenomenon of assortative
mixing, whereby nodes prefer to connect to others that are similar to
themselves, has been widely studied, but here we go further and examine how and
to what extent nodes that are otherwise similar can have different preferences.
Many individuals in a friendship network, for instance, may prefer friends who
are roughly the same age as themselves, but some may display a preference for
older or younger friends. We introduce a network model that captures this
behavior and a method for fitting it to empirical network data. We propose
metrics to characterize the mean and variation of mixing patterns and show how
to infer their values from the fitted model, either using maximum-likelihood
estimates of model parameters or in a Bayesian framework that does not require
fixing any parameters.
