library(ggplot2)
oldFaithfulPlot = ggplot(faithful, aes(eruptions,waiting))
oldFaithfulPlot + layer(geom="point")
oldFaithfulPlot + layer(geom="point") + layer(geom="smooth")


ggplot()+ layer(data=df, mapping=aes(x=ind, y=dep), geom="point",stat="identity",position_dodge(width=3))