R/days_in_fq.R

In PublicHealthEngland/hcaidcs: R functions for the mandatory surveillance of bacteraemia and C. difficile infection

#' Get the number of days in the quarter of a financial year
#'
#' For working with KH03, quarters are in format "yyyyq".
#' Want number of days per quarter and this varies by leap year.
#' This method takes leap year into account.
#'
#' \strong{Note:} This function must be used in conjunction with \code{\link[dplyr]{rowwise}} from dplyr or \code{\link[base]{sapply}}.
#' @param  x A financial year quarter in format "yyyyq"
#' @return The number of days in the quarter, accounting for leap years.
#' @examples
#' days_in_fq("20131")
#' days_in_fq("20134")
#' # 2016 is a leap year, should have 91 days in quarter 1 (i.e. 20154)
#' days_in_fq("20154")
#' x <- data.frame(fyear = c(20151, 20152, 20153, 20154))
#' x$days <- days_in_fq(x$fyear)
#' @export

days_in_fq <- function(x){
  if (!requireNamespace("lubridate", quietly = TRUE)) {
    stop("lubridate is needed for this function to work. Please install it.",
         call. = FALSE)
  }
  the_year <- lubridate::dmy(paste0("01-01-", as.numeric(substr(as.character(x),1,4)) + 1 )) # plus one, because for fy 2014, q4 is jan-mar 2015
  the_qtr <- as.numeric(substr(as.character(x), 5,5))
  days <- ifelse(the_qtr == 4,
                 31 + 28 + 31 + lubridate::leap_year(the_year),
                 ifelse(the_qtr == 1,
                        30 + 31 +30,
                        ifelse(the_qtr == 2,
                               31 + 31 + 30,
                               ifelse(the_qtr == 3,
                                 31 + 30 + 31,
                                 NA
                  )
           )))
  return(days)
}