Add events with time frame to plot.gantt()

gistfile1.r

# Function definition
add_event <- function(start, end = NULL, label = NULL, line = 0.5, las = 1, col = scales::alpha("steelblue", 0.5)) {
  if(is.null(end)) {
    end <- paste(start, "23:59:59")
    start <- paste(start, "00:00:00")
  }
  
  start <- as.POSIXct(start)
  end <- as.POSIXct(end)
  
  rect(start, 0, end, 100, col = col, border = FALSE)
  mtext(label, at = mean.POSIXct(c(start, end)), line = line, las = las, cex = 0.9)
  invisible(0)
}

# Example
library("plan")
data("gantt")
plot(gantt)

add_event(start = "2008-12-24", label = "X-Mas", col = "red")
add_event(start = "2008-06-15", end = "2008-07-15", label = "Summer vacation")