Social Network Analysis

1
Social Network Analysis

• UCINET

2
UCINET--Introduction

• UCINETUCINET is produced by Analytic
  Technologies. It offers a very user-friendly,
  reasonably priced software system for network
  analysis.
• Throughout this discussion, well use the example
  of the cosponsorship network of the 58
  legislators in the lower house of the Arizona
  legislature, 2001.

3
Starting UCINET

• When you first open UCINET, set the default
  directory to a directory of your choice, by
  typing in the directory name (into the space at
  the bottom edge of the UCINET window). Note that
  the original default directory is just the c\
  drive.
• Note that UCINET produces many types of filesand
  deleting any (before you are entirely done with
  your analysis) may make it difficult to use some
  of the others.

4
How to Read Data into UCINET

• There are several ways to read network data into
  UCINET. Ill review two basic methods?using
  matrices, and using dl language.
• UCINET can read in a matrix dataeither saved in
  a text file, or saved in excel.
• So, in the case of the Arizona cosponsorship data
  that we will use as an example, there are 58
  legislators and therefore 58 X 58 3,364
  dyads.

5
How to Read Data into UCINET

• If those data are saved in a text file (with 58
  rows, and 58 cosponsorship frequencies listed
  on each of those rows), they can be read in as
  raw data into UCINET.
• Arizona.txt is an example of such a file.
• Download this file. Then, in UCINET, click on
  Data and Import and Raw. The text box
  should allow you to search for the file youve
  downloaded, and to read it into UCINET.

6
How to Read Data into UCINET

• One way to double check that it is correct is
  to look at the number of rows and columns that
  are automatically filled into that dialogue box
  it should be 58.
• After youve read in the data, an output screen
  will show you the data in matrix form.
• You can also see the data in matrix form by going
  to Data, clicking on Spreadsheets, then clicking
  on Matrix. This will open up an emptry
  spreadsheet window. Click File and then Open
  (or, control-O) to open the file. The file is in
  the default directory (as specified in the lower
  row of the UCINET program), and it is called
  Arizona.h.

7
How to Read Data into UCINET

• An alternative is to read data in using a
  standard excel file. An example of such an excel
  file can be found here.
• In UCINET, go to Data, then Import, then Excel
  matrix. Be sure to tell UCINET whether the
  matrix includes row / column labels.
• (The UCINET program will immediately remind you
  of the name of the programjust as a safety
  double-check. Just click ok.)

8
How to Read Data into UCINET

• Often, the easiest way to read data into UCINET
  is to use DL language. A document with a set of
  examples of DL programming can be found here.
• When you use DL language, the default value of
  the edge between each possible pair of nodes is
  automatically set to 0 (that is, no connection).
  
• The DL language is then used to specify the value
  of all edges. Labels for the rows and columns of
  the matrix can also be specified through DL
  language.

9
How to Read Data into UCINET

• Some researchers find excel files easier to work
  withsome find DL language easier. In the
  Arizona case, the SAS program that I used
  actually creates a matrix file that is relatively
  easy to transfer into DL language.
• DL language can also be useful if you need to
  read in additional matrices. In the
  cosponsorship example, I have an additional
  matrix file that lists the number of shared
  committees on which each pair of legislators
  serve.

10
Other Types of Data

• Network files can be thought of in terms of
  matrices (whether or not they are actually read
  in as matrices (versus DL language)).
• A second type of file is an attribute file,
  which lists attributes for each node. So, I have
  a set of attributes for each legislator,
  including race, sex, partisanship, seniority, etc.

11
Reading in Attribute Files

• Reading in attribute files to UCINET is a bit
  unwieldy. Well use two examples from the
  Arizona legislative dataset?party (srepub,
  coded 1 if Republican, 0 otherwise) and ideology
  (measured by swnom01, a w-nominate score).
• Download the two excel files srepub and
  swnom01.

12
Reading in Attribute Files

• Notice that the files are in matrix formthere
  are 58 legislators in this network, so each of
  these two files has 58 rows and 58 columns. It
  is really only the first column that mattersthe
  other columns are just filler columns (as UCINET
  works only with matrix files.)
• Read the two files into UCINET, as you did with
  the cosponsorship file previously. In this case,
  however, choose node attribute file rather than
  network adjacency matrix.
• At that point, you should have srepub.h (and
  the companion file srepub.d) as well as
  swnom01.h (and the companion file swnom01.d).

13
Reading in Attribute Files

• In order to create an attribute measure, go to
  Data, then click on Attribute. Browse to find
  the srepub.h that you imported into UCINET
  (after downloading the parallel excel file).
• The attribute information for Republican is in
  the first column (recall what the excel file
  looked likethe first column was 0/1 (0Dem,
  1Repub), and the other 57 columns were 99 to
  just fill out the matrix.

14
Reading in Attribute Files

• So, for Vector is Row or Column?, choose
  column. For Which Row/Col, choose 1.
• Now, you need to specify how you want the
  attribute to be constructed. In this case, it
  makes sense to create an attribute that stands
  for exact matchestwo legislators who have the
  same code will be of the same party (either both
  Republican or both Democrat).

15
Reading in Attribute Files

• So, under Method, select Exact Matches
• And the output data set defaults to
  srepub-Column-1. It may be useful to rename it
  to something that makes more intuitive sense,
  such as sameparty

16
Reading in Attribute Files

• Next, lets look at ideology as an attribute
  (swnom01).
• As before, enter in the name of the file (browse
  to find wherever you saved the ideology file that
  you imported into UCINET, after downloading the
  relevant excel file from the web.) And, enter in
  Column and 1 to specify that the attribute
  info can be found in the first column of data in
  the file.

17
Reading in Attribute Files

• However, it no longer makes sense to choose
  exact matches, since legislators will rarely be
  exactly the same ideologywhat matters is how
  close they are in ideology. So, in Method,
  choose absolute differencewhich will represent
  similarity between two legislators ideologies.

18
Reading in Attribute Files

• And, it may make sense to name the output file
  something that makes intuitive sense, such as
  diffideol.
• Okay, now what can we do with UCINET?

19
UCINET

• As noted in previous discussions, UCINET has a
  terrific tutorial. You can use the Arizona data
  to practice reading in files, and calculating out
  commonly used descriptives for networks and nodes
  (such as the various centrality measures that
  weve discussed.)

20
QAP Procedure

• UCINET also allows the possibility of a
  regression analysis, using a QAP procedure.
• The QAP Procedure will be the focus of our next
  discussion.