question on plot in R with mac

Hello all

My computer is MacBook and I want to draw a plot in R, for example for
x <- c(1,3,6,9,12)
y <- c(1.5,2,7,8,15)
 I use this command plot(x,y) to do but I see this massage:
 Erreur dans plot(Di, g) :
  argument(s) inutilis?(s) (c(1, 2, 3), c(12, 23, 34))

Could you please help me?

Thank you
khazaei