Scaling Roll Call Votes with W-NOMINATE in R

21 Pages Posted: 6 Oct 2008 Last revised: 21 May 2013

See all articles by Keith T. Poole

Keith T. Poole

University of Georgia - School of Public and International Affairs

Jeffrey B. Lewis

University of California, Los Angeles (UCLA)

James Lo

University of California, Los Angeles (UCLA) - Department of Political Science

Royce Carroll

University of Essex - Department of Government

Date Written: September 30, 2008

Abstract

This paper presents a software package designed to estimate Poole and Rosenthal W-NOMINATE scores in R. The package uses a logistic regression model to analyze political choice data, usually (though not exclusively) from a legislative setting. In contrast to other scaling methods, W-NOMINATE explicitly assumes probabilistic voting based on a spatial utility function, where the parameters of the utility function and the spatial coordinates of the legislators and the votes can all be estimated on the basis of observed voting behavior. Building on the W-NOMINATE software written by Poole in FORTRAN, the new package facilitates easier data input and manipulation, generates bootstrapped standard errors, and includes a new suite of graphics functions to display the results. We demonstrate the functionality of this package by conducting a natural experiment using roll calls - an experiment which is greatly simplified by the data manipulation capabilities of the W-NOMINATE package in R.

Keywords: multivariate, R, roll call, scaling, wnominate

Suggested Citation

Poole, Keith T. and Lewis, Jeffrey B. and Lo, James and Carroll, Royce, Scaling Roll Call Votes with W-NOMINATE in R (September 30, 2008). Available at SSRN: https://ssrn.com/abstract=1276082 or http://dx.doi.org/10.2139/ssrn.1276082

Keith T. Poole (Contact Author)

University of Georgia - School of Public and International Affairs ( email )

Baldwin Hall
Athens, GA 30602-6254
United States

Jeffrey B. Lewis

University of California, Los Angeles (UCLA) ( email )

405 Hilgard Avenue
Box 951361
Los Angeles, CA 90095
United States

James Lo

University of California, Los Angeles (UCLA) - Department of Political Science ( email )

Loas Angeles, CA
United States

Royce Carroll

University of Essex - Department of Government ( email )

Wivenhoe Park
Colchester CO4 3SQ, CO4 3SQ
United Kingdom

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