R/uniqueValues.R

In replyr: Patches to Use 'dplyr' on Remote Data Sources

# Contributed by John Mount jmount@win-vector.com , ownership assigned to Win-Vector LLC.
# Win-Vector LLC currently distributes this code without intellectual property indemnification, warranty, claim of fitness of purpose, or any other guarantee under a GPL3 license.

#' @importFrom dplyr ungroup mutate summarize
NULL



#' Compute number of unique values for each level in a column.
#'
#' @param x tbl or item that can be coerced into such.
#' @param cname name of columns to examine, must not be equal to 'replyr_private_value_n'.
#' @return unique values for the column.
#'
#' @examples
#'
#' d <- data.frame(x=c(1,2,3,3))
#' replyr_uniqueValues(d,'x')
#'
#' @export
replyr_uniqueValues <- function(x, cname) {
  if((!is.character(cname))||(length(cname)!=1)||(cname[[1]]=='replyr_private_value_n')) {
    stop('replyr_uniqueValues cname must be a single string not equal to "replyr_private_value_n"')
  }
  replyr_private_value_n <- NULL # false binding for 'replyr_private_value_n' so name does not look unbound to CRAN check
  REPLYRGROUPINGCOL <- NULL # declare not an unbound variable
  wrapr::let(
    c(REPLYRGROUPINGCOL=cname),
    x %.>%
      dplyr::ungroup(.) %.>%
      replyr_select(., cname) %.>%
      dplyr::mutate(., replyr_private_value_n=1.0) %.>%
      dplyr::group_by(., REPLYRGROUPINGCOL) %.>%
      dplyr::summarize(., replyr_private_value_n=sum(replyr_private_value_n)) -> res
  )
  # Can't get rid of the warning on MySQL, even suppressWarnings() doesn't shut it up
  res
}