aRgh What you should know about R to prevent any frustration. Gems Accessing Private Variables or Functions Use ::: in conjuction with a library such as ggplot2:::. Adding significance manually to ggplot2 plots geom_signif(annotations = c(formatC("*"),formatC("*")), y_position = c(1.5, 2.5), xmin=c(1, 2), xmax=c(3, 3))