Using ggplot function in R error : could not find function ggplot

Question

I have installed ggplot and ggplot2 and their dependencies, but I cannot use the function ggplot; whenever I try to use it I get

Error in gg

Answer 1

Try:

library(ggplot2)

Even after installing a package, you have to load a package each time you load R.

This question is answered comprehensively in the r-faq:

Error: could not find function ... in R