MNP: Fitting the Multinomial Probit Model

#' Voters' Preferences of Political Parties in Japan (1995)
#' 
#' This dataset gives voters' preferences of political parties in Japan on the
#' 0 (least preferred) - 100 (most preferred) scale.  It is based on the 1995
#' survey data of 418 individual voters.  The data also include the sex,
#' education level, and age of the voters. The survey allowed voters to choose
#' among four parties: Liberal Democratic Party (LDP), New Frontier Party
#' (NFP), Sakigake (SKG), and Japanese Communist Party (JCP).
#' 
#' 
#' @name japan
#' @docType data
#' @format A data frame containing the following 7 variables for 418
#' observations.
#' 
#' \tabular{llll}{ LDP \tab numeric \tab preference for Liberal Democratic
#' Party \tab 0 - 100 \cr NFP \tab numeric \tab preference for New Frontier
#' Party \tab 0 - 100 \cr SKG \tab numeric \tab preference for Sakigake \tab 0
#' - 100 \cr JCP \tab numeric \tab preference for Japanese Communist Party \tab
#' 0 - 100 \cr gender \tab factor \tab gender of each voter \tab \code{male} or
#' \code{female} \cr education \tab numeric \tab levels of education for each
#' voter \tab \cr age \tab numeric \tab age of each voter \tab }
#' @keywords datasets
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