data(nottem)
n_years <- length(nottem)/12
nottem_month <- rep(1:12, times=n_years)
nottem_year <- rep(1920:(1920+n_years-1),each=12)
nottem_plot <- qplot(nottem_month,nottem, 
                    colour=factor(nottem_year), 
                    geom="line") + theme_bw()
print(nottem_plot)