R/limit_days.R

In pollyvote/pollyvoter: Aggregate Components, Calculate Forecasts and Determine Errors for Election Results.

#' limit days in a data set
#' 
#' internal function that handles missing values in the data frame of a pollyvote 
#' object. Different error handling arguments can be handed over.
#' If \code{election_data}, \code{election} and \code{election_date} are supplied to the function, than 
#' the election date which is supplied will be used
#' and resolving of the election date from
#' \code{get_election_result(pv, election_name = election)} will be ignored.
#' 
#' If limit_days is called like: limit_days(pv$data, no_days = 10, election_date = "Y-M-DD")
#' and if pv object is not supplied,
#' then election_date will not be validated whether it is existing election date in the pollyvote object.
#' Therefore, it is more safe for if pollyvote object is also supplied as an argument 
#' (e.g. limit_days(pv$data, no_days = 10, pv = pv, election_date = "Y-M-DD")).  
#' 
#' @param data [\code{data.frame()}]\cr
#'   data frame of a pollyvote object.
#' @param no_days [\code{integer(1)}]\cr
#'   number of days before the election to return results for.
#' @param election_data [\code{data.frame()}]\cr
#'   data frame containing the election results. The election date is included in the \code{date} coulmn.
#' @param pv [\code{pollyvote(1)}]\cr
#'   pollyvote container to extract the \code{election} from.
#' @param election [\code{character(1)}]\cr
#'   name of the election from \code{pv$election_result} to use.
#' @param election_date [\code{character(1)}]\cr
#'   date of the election in the format '\%Y-\%m-\%d'. If not supplied, the date of the election has to be supplied in the election data.
#' @param ... [\code{list()}]\cr
#'   additional arguments, currently ignored.
#' 
#' @return the data set limited to the number of days before the election.
#'
#' @export
limit_days = function(data, no_days, election_data, pv, election, 
                      election_date, ...) {
  assert_class(data, "data.frame")
  # check if anything has to be done
  if (all(missing(no_days), missing(election_data), missing(pv), 
          missing(election), missing(election_date))) {
    return(data)
  }
  
  assert_numeric(no_days)
  if(!missing(election_data))
    assert_class(election_data, "data.frame")
  if(!missing(pv))
    assert_class(pv, "pollyvote")
  if(!missing(election) & !missing(pv))
    assert_choice(election, get_election_result(pv, election_name = election)$election)
  if(!missing(election_date)) {
    election_date = as.POSIXct(election_date, format = "%Y-%m-%d")
    if (!missing(pv)) {
      election_result = get_election_result(pv, election_date = election_date)
      if (nrow(election_result) == 0) {
        stop(paste("No election result exists for election date", election_date, sep = ": "))
      }
    }
  }
  
  # get election_data
  if (missing(election_data)){
    if (!missing(pv) & !missing(election))
      election_data = get_election_result(pv, election_name = election)
  }
  
  # get election date
  if (missing(election_date) & !missing(election_data)) {
    if ("date" %in% colnames(election_data)) {
      election_date = unique(election_data$date)
      if (length(election_date) != 1) {
        stop("Only one distinct date should be present in the election data.")
      }
    }
    else {
      warning("limit_days could not find out the date of the election. Please specify the argument election_date.")
      return(data)
    }
  } 
  
  # subset the data accordingly
  earliest_date = election_date - as.difftime(no_days, units = "days")
  data = filter(data, date > earliest_date)
  return(data)
}