"Since some student asked to me some information about ggplot, I write it here for everybody.
If you are interested to plots and a graphic quality superior to the standard R, you can utilize the R package ggplot2 !!
Here they are some resources that I want to I would advise to use in your learning process:
1) First a good manual
and then, these other sites about ggplot I often use:
2) the official site:
3) a quick cookbook with examples and code snippets
PS: many other resources here: