balls <- 1:50000 tennis <- rcauchy(50000, 0, 1) averages <- cumsum(tennis)/balls window <- function(time) { duration <- time:(time+999) plot(balls[duration], tennis[duration], pch=".", ylim=c(-5,5)) points(balls[duration], averages[duration], type="l") Sys.sleep(0.02) } ignore <- sapply((1:490)*100, window) plot(balls, averages, type="l")