rlegend is a version of legend for R that implements
  plot=FALSE, adds grid=TRUE, and defaults lty,
  lwd, pch to NULL and checks for length>0
  rather than missing(), so it's easier to deal with
  non-applicable parameters.  But when grid is in effect, the
  preferred function to use is rlegendg, which calls the
  lattice draw.key function.
rlegend(x, y, legend, fill, col = "black", lty = NULL, lwd = NULL,
        pch = NULL, angle = NULL, density = NULL, bty = "o",
        bg = par("bg"), pt.bg = NA, cex = 1, xjust = 0, yjust = 1,
        x.intersp = 1, y.intersp = 1, adj = 0, text.width = NULL,
        merge = do.lines && has.pch, trace = FALSE, ncol = 1,
        horiz = FALSE, plot = TRUE, grid = FALSE, …)rlegendg(x, y, legend, col=pr$col[1], lty=NULL,
         lwd=NULL, pch=NULL, cex=pr$cex[1], other=NULL)
see legend
set to FALSE to suppress drawing the legend.  This
    is used the compute the size needed for when the legend is drawn
    with a later call to rlegend.
set to TRUE if the grid package is in effect
see legend
a list containing other arguments to pass to
    draw.key.  See the help file for xyplot.
a list with elements rect and text.  rect has
  elements w, h, left, top with size/position information.