[r] Combine Points with lines with ggplot2

A small change to Paul's code so that it doesn't return the error mentioned above.

dat = melt(subset(iris, select = c("Sepal.Length","Sepal.Width", "Species")),
           id.vars = "Species")
dat$x <- c(1:150, 1:150)
ggplot(aes(x = x, y = value, color = variable), data = dat) +  
  geom_point() + geom_line()