Code highlight themes in knitr: "lucretia"

plot.leaf <- function(n = 50000, col = "green", cex = 2) {
    x <- c(0.5, 0.5)
    plot(x[1], x[2], xlim = c(-3, 3), ylim = c(0, 10), type = "n", xlab = "",
        ylab = "")
    p <- c(0.85, 0.92, 0.99, 1)
    A <- rbind(c(0.85, 0.04), c(-0.04, 0.85), c(0.2, -0.26), c(0.23, 0.22),
        c(-0.15, 0.28), c(0.26, 0.24), c(0, 0), c(0, 0.16))
    B <- cbind(c(0, 1.6), c(0, 1.6), c(0, 0.44), c(0, 0))

    for (i in 1:n) {
        ran <- runif(1)
        ind <- rank(c(p, ran), ties.method = "min")[5]
        x <- A[(2 * ind - 1):(2 * ind), ] %*% x + B[, ind]
        points(x[1], x[2], pch = ".", cex = cex, col = col)
    }
}
## plot leaf
par(mar = c(0, 0, 0, 0) + 0.1)
plot.leaf(cex = 1.6)
box()

1 + 1

sqrt(-1)  # warning

message("knitr says hello to HTML!")  # message

1 + "a"  # error