RDigram: Analysis of Items from Tests and Surveys

#' @title Physical functioning subscale
#' @description The dataset originated in a Danish Health survey. This is the SF36 subscale measuring physical functioning.
#' @docType data
#' @keywords datasets
#' @name pf3
#' @usage data(pf3)
#' @return pf3 is an object of class digram.object.
#' @format A data frame with 1049 rows and 25 variables of which 12 are used.
#' The scale summarizes responses to the following ten items:
#' \describe{
#' Does your health now limit you in these activities? If so, how much?
#' \item{A}{PF1: Vigorous activities}
#' \item{B}{PF2: Moderate activities}
#' \item{C}{PF3: Lifting or carrying groceries}
#' \item{D}{PF4: Climbing several flights of stairs}
#' \item{E}{PF5: Climbing one flight of stairs}
#' \item{F}{PF6: Bending, kneeling, or stooping}
#' \item{G}{PF7: Walking more than a mile}
#' \item{H}{PF8: Walking several blocks}
#' \item{I}{PF9: Walking one block}
#' \item{J}{PF10: Bathing or dressing yourself}
#' The responses to these questions were coded in the following way:
#' \item{0}{Limited a lot}
#' \item{1}{Limited a little}
#' \item{2}{Not limited}
#' so that a low score indicates physical impairment. Gender and Age are also included in this project.
#' }
#' @source The \code{pf3} data were obtained from
#' Kreiner, S. (2003). *Introduction to DIGRAM*. Dept. of Biostatistics, University of Copenhagen.
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