R/addShadedNight.R

In PWFSLSmoke: Utilities for Working with Air Quality Monitoring Data

#' @export
#' @importFrom grDevices adjustcolor
#' @importFrom graphics rect par
#' @title Add Nighttime Shading to a Plot
#' @param timeInfo dataframe with local time, sunrise, and sunset
#' @param col color used to shade nights -- defaults to \code{adjustcolor('black',0.2)}
#' @description Draw shading rectangles on a plot to indicate nighttime hours.
#' @seealso \link{timeInfo}

addShadedNight <- function(timeInfo, col=adjustcolor('black',0.1)) {
  
  localTime <- timeInfo$localTime
  sunrise <- timeInfo$sunrise[!duplicated(timeInfo$sunrise)]
  sunset <- timeInfo$sunset[!duplicated(timeInfo$sunset)]
  
  # Sanity check
  if (any(sunset < sunrise)) {
    stop('sunset before sunrise!!!')
  }
  
  # Left edge to first sunrise
  if ( localTime[1] < sunrise[1] ) {
    rect(par('usr')[1], ybottom=par('usr')[3], 
         xright=sunrise[1], ytop=par('usr')[4], 
         col=col, border=NA)
  }
  
  # Complete nights
  if ( length(sunset) > 1 ) {
    for (i in seq(length(sunset)-1)) {
      rect(xleft=sunset[i], ybottom=par('usr')[3], 
           xright=sunrise[i+1], ytop=par('usr')[4], 
           col=col, border=NA)              
    }
  }
  
  # Last sunset to right edge
  rect(xleft=sunset[length(sunset)], ybottom=par('usr')[3], 
       xright=par('usr')[2], ytop=par('usr')[4], 
       col=col, border=NA)        
  
}