R/add_prop.R

In sarid-ins/saridr: An R package for common tasks related to market research analysis via R

#' Compute the proportion of items (like dplyr::add_count() does with number of appearances)
#'
#' @param x a tbl() to compute proportions
#' @param leave_n if TRUE will also generate a column named n4prop (FALSE by default).
#' @param name The output column name. If omitted, it will be prop.
#' @param ... Variables to group by
#'
#' @return A tbl, grouped the same way as x.
#'
#' @examples
#' # Without any grouping, just calc proportions
#' mtcars %>% add_prop(cyl)
#' # Number of variables
#' mtcars %>% add_prop(cyl, vs)
#' # To compute the proportions relative to a variable, use a group_by
#' mtcars %>% group_by(am) %>% add_prop(cyl, vs)
#'
#' @importFrom magrittr %>%
#'
#' @export
add_prop <- function(x, ..., leave_n = FALSE, name = "prop"){

  tmp <- x %>% dplyr::count(..., name = "n4prop") %>%
    dplyr::mutate(`:=`(!!name, n4prop/sum(n4prop)))

  if (!leave_n) {
    tmp <- tmp %>% dplyr::select(-n4prop)
  }

  suppressMessages(
    res <- x %>%
      left_join(tmp)
  )

  return(res)

}