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# 16: Multiplex Networks

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In this chapter we will look at some of the tools that social network analysts have used to grapple with the complexity of analyzing simultaneous multiple relations among actors. We'll begin by examining some basic data structures for multiplex data, and how they can be visualized. To be useful in analysis, however, the information about multiple relations among a set of actors must somehow be represented in summary form. There are two general approaches: reduction and combination. The "reduction" approach seeks to combine information about multiple relations among the same set of actors into a single relation that indexes the quantity of ties. All of these issues are dealt with in the section on multiplex data basics.

• 16.1: Introduction to Multiplex Networks
Sociologists tend to assume, until proven otherwise, that actors' behavior is strongly shaped by the complex interaction of many simultaneous constraints and opportunities arising from how the individual is embedded in multiple kinds of relationships. The characteristics and behavior of whole populations, as well, may depend on multiple dimensions of integration/cleavage. Solidarity may be established by economic exchange, shared information, kinship, and other ties operating simultaneously.
• 16.2: Multiplex Data Basics
Multiplex data are data that describe multiple relations among the same set of actors. The measures of the relations can be directed or not; and the relations can be recorded as binary, multi-valued nominal, or valued (ordinal or interval).
• 16.3: Role Algebra for Mulitplex Data
The notion of a "role algebra" is to understand the relations between actors as realizations of the logically possible "compounds" of relations of selected path lengths. Most often in network analyses, we focus on path of length one (two actors are connected or not).
• 16.S: Multiplex Networks (Summary)
The actors in the kinds of networks that social scientists study are very frequently connected by more than one type of tie, simultaneously. That is, the relationship between any two actors may be multiplex. In this chapter, we've introduced a few of the tools that are commonly used to help to make sense of the complex patterns of embedding that can emerge when there is more than one kind of tie operating simultaneously.