Add colored rectangle as background to a xts time-series (R language)

addPolySeq.R

addPolySeq <- function(tval, y, ylim, ...){
  i <- seq(1, by = 2, to = length(tval)- 1)
  tval_p <- cbind(tval[i], tval[i + 1])
  u <- (apply(tval_p, 1, FUN, y = y, ylim = ylim, ...))
  u
}
FUN <- function(x, y, ylim, ...){
  ynew <- y[paste0(c(as.Date(x[1]), as.Date(x[2])), collapse = "/")]
  nr <- nrow(ynew)
  if(nr > 0){
    shade <- cbind(upper = rep(ylim[2], nr), lower = rep(ylim[1], nr))
    shade <- xts(shade, index(ynew)) 
    addPolygon(shade, ...)
  }
}

 

plot(ps)
tval <- seq(as.Date("2014-02-01"), length=35, by="quarters")
addPolySeq(tval, y = ps, ylim = c(0, 100), on = -1, col = "dodgerblue")