outside_legend.R

# from https://stackoverflow.com/questions/3932038/plot-a-legend-outside-of-the-plotting-area-in-base-graphics,
# a way to add a legend outside of the plot area
outside_legend <- function(...) {
    opar <- par(fig=c(0, 1, 0, 1), oma=c(0, 0, 0, 0), 
                mar=c(0, 0, 0, 0), new=TRUE)
    on.exit(par(opar))
    plot(0, 0, type='n', bty='n', xaxt='n', yaxt='n')
    legend(...)
}