Add a format argument to extract_fin_year()

This argument keeps the default format (so existing code will work without modification) and allows for choosing a numeric (integer) output.

R/extract_fin_year.R

@@ -5,32 +5,53 @@
 #'
 #' @details The PHS accepted format for financial year is YYYY/YY e.g. 2017/18.
 #'
-#' @param date A date which must be supplied with `Date`, `POSIXct`, `POSIXlt` or 
+#' @param date A date which must be supplied with `Date`, `POSIXct`, `POSIXlt` or
 #' `POSIXt` class. [base::as.Date()],
 #' [`lubridate::dmy()`][lubridate::ymd] and
 #' [`as.POSIXct()`][base::as.POSIXlt] are examples of functions which
 #' can be used to store dates as an appropriate class.
 #'
+#' @param format The format to return the Financial Year
+#'  * (Default) As a character vector in the form '2017/18'
+#'  * As an integer e.g. 2017 for '2017/18'.
+#'
 #' @return A character vector of financial years in the form '2017/18'.
 #'
 #' @examples
 #' x <- lubridate::dmy(c(21012017, 04042017, 17112017))
 #' extract_fin_year(x)
 #' @export
-extract_fin_year <- function(date) {
+extract_fin_year <- function(date, format = c("full", "numeric")) {
   if (!inherits(date, c("Date", "POSIXt"))) {
     cli::cli_abort("{.arg date} must be a {.cls Date} or {.cls POSIXt} vector,
                    not a {.cls {class(date)}} vector.")
   }
 
-  # Note: lubridate year and month coerce to double
-  # We only need integers for our purposes
-  posix <- as.POSIXlt(date, tz = lubridate::tz(date))
-  y <- posix$year + 1900L
-  m <- posix$mon
-  fy <- y - (m < 3L)
-  next_fy <- (fy + 1L) %% 100L
-  out <- sprintf("%.4d/%02d", fy, next_fy)
-  out[is.na(date)] <- NA_character_
-  out
+  if (missing(format)) {
+    format <- "full"
+  } else {
+    format <- match.arg(format)
+  }
+
+  if (inherits(date, "POSIXlt")) {
+    posix <- date
+  } else {
+    posix <- as.POSIXlt(date, tz = lubridate::tz(date))
+  }
+
+  year <- posix$year + 1900L
+  month <- posix$mon
+  fy_num <- year - (month < 3L)
+
+  if (format == "numeric") {
+    return(fy_num)
+  }
+
+  next_fy <- (fy_num + 1L) %% 100L
+
+  fin_year_chr <- sprintf("%.4d/%02d", fy_num, next_fy)
+
+  fin_year_chr[is.na(date)] <- NA_character_
+
+  return(fin_year_chr)
 }