make_wer.R

x <- rnorm(100)
x.mean <- mean(x)
x.sd <- sd(x)

bands <- sapply(seq(-3, 3), function(i) {i * rep(x.sd, 100) })
cols <- c("red", "orange", "gold", "green", "gold", "orange", "red")
plot(x, ylim=c(-3.5, 3.5), type="l", lty=2, main="Western Eletric Rules")
for (i in 1:7) {
  lines(x.mean + bands[,i], col=cols[i], lwd=2, lty=2)
  # there is no Zone 0
  if (i!=4) {
    text(50, x.mean + bands[1,ifelse(i > 4, i-1, i)] + 0.5, paste("Zone", i-4),cex=1.5)    
  }
}