draw footprints for fun...

footprint.R

foot = function(x, y, ...) {
    points(x, y, cex = 10, ...)
    points(x, y + 2, cex = 5, ...)
    points(x - 0.4, y + 1.2, cex = 7, ...)
    points(x + 0.4, y + 1.2, cex = 4, ...)
} 
for (j in 1:3) {
    x = sample(seq(1, 30, 3))
    plot(x)
    for (i in 1:10) {
        foot(i, x[i], pch = 19)
        Sys.sleep(0.5)
    }
}