feat: get the number of days in a month

NAMESPACE

@@ -1,5 +1,6 @@
 # Generated by roxygen2: do not edit by hand
 
+export(number_of_days)
 importFrom(grDevices,dev.off)
 importFrom(grDevices,pdf)
 importFrom(graphics,par)

R/number_of_days.R

@@ -0,0 +1,67 @@
+#' Return the number of days in a month for a given year
+#'
+#' @param date either a `character` or a `Date` of length 1. See examples below.
+#' 
+#' @param format a `character` of length 1. Used to specify the format of the 
+#'   date. Default is `"%Y-%m-%d"` (i.e. 2024-12-25). See examples below.
+#'
+#' @return An `integer` corresponding to the number of days in the month for 
+#' the specified year.
+#' 
+#' @export
+#'
+#' @examples
+#' ## Default ----
+#' number_of_days("2024-02-01")
+#' 
+#' ## Day doesn't matter ----
+#' number_of_days("2024-02-23")
+#' 
+#' ## Year matters ----
+#' number_of_days("2023-02-23")
+#' 
+#' ## Change the format ----
+#' number_of_days("2024/02/23", format = "%Y/%m/%d")
+#' 
+#' ## French format ----
+#' number_of_days("23/02/2024", format = "%d/%m/%Y")
+
+number_of_days <- function(date, format = "%Y-%m-%d") {
+
+  if (missing(date)) {
+    stop("Argument 'date' is required", call. = FALSE)
+  }
+
+  if (!is.character(date) && !inherits(date, "Date")) {
+    stop("Argument 'date' must be either a character or a Date", call. = FALSE)
+  }
+
+  if (length(date) != 1) {
+    stop("Argument 'date' must be of length 1", call. = FALSE)
+  }
+
+  if (nchar(as.character(date)) != 10) {
+    stop("Wrong 'date'. Year must have 4 characters (e.g. 2024), month 2 ", 
+         "characters (e.g. 01), and day 2 characters (e.g. 01)", call. = FALSE)
+  }
+
+  if (is.character(date)) {
+    date <- as.Date(date, format = format)
+  }
+
+
+  if (is.na(date)) {
+    stop("Error in converting 'date'. Please use the argument 'format' to ", 
+         "specify the appropriate format. See '?strptime' for further ", 
+         "information", call. = FALSE)
+  }
+
+  month <- format(date, format = "%m")
+
+  while (format(date, format = "%m") == month) {
+
+    date <- date + 1
+  }
+
+  as.integer(format(date - 1, format = "%d"))
+}