library(grImport)



grid.moonPhase <- function(x, y, phase, size=unit(.05, "in")) {
  n <- 17
  angle <- seq(0, 2*pi, length=n)
  xx <- x + cos(angle)*size
  yy <- y + sin(angle)*size
  if (phase == "New")
    fill <- "black"
  else
    fill <- "white"
  grid.polygon(xx, yy, gp=gpar(fill=fill))
  if (phase == "1Q")
      grid.polygon(xx[(n/4):(n*3/4) + 1],
                   yy[(n/4):(n*3/4) + 1],
                   gp=gpar(fill="black"))
  if (phase == "3Q")
      grid.polygon(xx[c(1:(n/4 + 1), (n*3/4 + 1):n)],
                   yy[c(1:(n/4 + 1), (n*3/4 + 1):n)],
                   gp=gpar(fill="black"))
}

# grid.newpage()
pushViewport(viewport(gp=gpar(cex=0.7)),
             plotViewport(c(4, 5, 3, 1)),
             dataViewport(as.numeric(lowTideDate), 
                          as.numeric(mainHours)))
vectorMoon <- 
    grImport::readPicture(system.file("extra", "comic_moon.ps.xml",
                            package="RGraphics"))
grImport::grid.picture(vectorMoon)
grid.segments(unit(phases$date, "native"), 0,
              unit(phases$date, "native"), 1,
              gp=gpar(lty="dashed"))
for (subset in list(1:13, 14:29, 30:31)) {
  grid.lines(lowTideDate[subset], lowTideHour[subset],
             default.units="native", 
             gp=gpar(lwd=2))
  grid.points(lowTideDate[subset], lowTideHour[subset],
              pch=16, size=unit(2, "mm"))
}
grid.rect(gp=gpar(fill=NA))
xTicks <- seq(min(lowTideDate), max(lowTideDate), by="week")
grid.xaxis(at=xTicks, label=format(xTicks, "%b %d"))
grid.yaxis(at=mainHours, label=format(mainHours, "%H:%M"))
grid.text("Time of Low Tide (NZDT)", 
          x=unit(-4, "lines"), rot=90)
grid.text("Auckland, New Zealand January 2010", 
          y=unit(-3, "lines"))
grid.xaxis(main=FALSE, at=phases$date, label=FALSE)
for (i in 1:nrow(phases))
    grid.moonPhase(unit(phases$date[i], "native"),
                   unit(1, "npc") + unit(1, "lines"), 
                   phases$phase[i])
grid.text("Phases of the Moon", 
          y=unit(1, "npc") + unit(2, "lines"))
popViewport(2)