W-NOMINATE is a scaling procedure that performs parametric unfolding of binary choice data. Given a matrix of binary choices by individuals (for example, Yes or No) over a series of Parliamentary votes, W-NOMINATE produces a configuration of legislators and outcome points for the Yea and Nay alternatives for each roll call using a probabilistic model of choice. It is discussed in detail in:

Download wnominate: W-NOMINATE Roll Call Analysis Software for R

W-NOMINATE in R Examples (R programs and datasets)

Download W-NOMINATE scores on the Data Download page