added function to put UK Whitsun publi choliday on a date plot

R/addWhitsunDate.R

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+#' \code{addWhitsunDate} adds extended weekend shading and label for UK Whit Sunday (late spring bank holiday) where x axis is a date. Should work in any time-zone
+#'
+#' @param p the plot to add them to
+#' @param yMin the smallest y value
+#' @param yMax the largest y value
+#' @author Ben Anderson, \email{b.anderson@@soton.ac.uk} (original)
+#' @export
+#'
+addWhitsunDate <- function(p, yMin, yMax){
+  p <- p + annotate("rect", xmin = as.Date("2020-05-23"),
+           xmax = as.Date("2020-05-26"), # 3 day weekend starting Saturday (in UK)
+           ymin = yMin, ymax = yMax,
+           alpha = gcParams$weAlpha, fill = gcParams$weFill) +
+    annotate("text", x = as.Date("2020-05-24"),
+             y = yMax*gcParams$labelPos,
+             label = "Whitsun 2020")
+  return(p)
+}