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**NETWORKS>CENTRALITY>GROUP CENTRALITY **

**PURPOSE **Calculate group degree centrality and group K-step reach centrality for specified groups.** **

**DESCRIPTION** The group degree centrality of a group of actors is the size of the set of actors who are directly connected to group members. This can be normalized by considering the size of the non-group member set. The group K-step reach is the number or proportion of non-group members that can be reached from a group member in K steps or less. Directed versions of both these measures can be constructed in the same was as for individual actor centralities. This routine takes an actor by group indicator matrix and calculates these measures for each group given in the columns of the matrix.

**PARAMETERS**

**Input Network:**

** **Name of file containing network to be analyzed. Data type: Graph.

**Input Groups (actor by group indicator matrix)**

Name of file containing group indicator matrix. The rows will correspond to the actors in the input network each column will specify a group. A 1 in row i col j indicates that actor i is a member of group j. All other entries should be zero.

**Output measurest:** (Default= <inputfilename>-grpcent)

Name of UCINET dataset containing group cntrality measures.

**Data are:**

** **Radio buttons to select directed, undirected or to let the program detect if the data are directed.

**Report**

** **A tick in the raw will give total numbers of actors for each measure. The normalized score will give the proportions.

**Measures**

** **Which measures to include, currently only degree and k-step reach are implemented.

**K **(Default=2)

Value of K to be used in the k-step reach.

**Degree options**

** **A tick in the count isolates means that isolates will be included as non-group members. This only affects the normalized option.

**Calculation Method**

** **Currently only the reduced method which shrinks each group to a single node is implemented.

**LOG FILE** A table which gives the group centrality scores selected for each group.

**TIMING **O(N^2).

**COMMENTS **

**REFERENCE **Everett, M.G. and Borgatti, S.P. (1999) The Centrality of Groups and Classes. Journal of Mathematical Sociology 23 181-202.