R/dummify.R

In lbraglia/lbmisc: Miscellaneous Utilty Functions

#' Generate a data.frame of dummy variables given a vector
#'
#' Generate a data.frame of dummy variables given a vector
#'
#' @param x a vector
#' @param prefix name prefix of returned \code{\link{data.frame}} columns
#' @return a \code{\link{data.frame}} to be used with \code{\link{cbind}}
#' @examples
#'
#' rep(1:3, 4)
#' dummify(rep(1:3, 4))
#'
#' @export
dummify <- function(x, prefix = "", keep_NA = TRUE){
    if ((xclass <- class(x)) %nin% c("integer", "factor", "ordered"))
        stop("only integer, factor or ordered vectors")
    
    if (! (is.character(prefix) && (length(prefix) == 1)))
        stop("prefix must be a 1-length character vector")
    
    if ("integer" == xclass)
        x <- factor(x)
    
    xlevels <- gsub(" ", "_", levels(x))
    res <- if (keep_NA){
               # https://stackoverflow.com/questions/5616210
               stats::model.matrix.lm(~ x - 1, na.action = 'na.pass')
           } else {
               stats::model.matrix(~ x - 1)
           }
    res <- as.data.frame(res)
    names(res) <- paste0(prefix, xlevels)
    res
}