3.3 Ejemplos

plot(cars)
abline(h = c(20, 40), lty = 2) # líneas horizontales discontinuas (lty=2)
# selecciona puntos y los dibuja en azul sólido
points(subset(cars, dist > 20 & dist < 40), pch = 16, col = 'blue') 

x <- seq(0, 2 * pi, length = 100)
y1 <- cos(x)
y2 <- sin(x)
plot( x, y1, type = "l", col = 2, lwd = 3, xlab = "[0,2pi]", ylab = "", main = "Seno y Coseno")
lines(x, y2, col = 3, lwd = 3, lty = 2)
points(pi, 0, pch = 17, col = 4)
legend(0, -0.5, c("Coseno", "Seno"), col = 2:3, lty = 1:2, lwd = 3)

abline(v = pi, lty = 3)
abline(h = 0, lty = 3)
text(pi, 0, "(pi,0)", adj = c(0, 0))

Alternativamente se podría usar curve():

curve(cos, 0, 2*pi, col = 2, lwd = 3, 
      xlab = "[0,2pi]", ylab = "", main = "Seno y Coseno")
curve(sin, col = 3, lwd = 3, lty = 2, add = TRUE)