> install.packages("ggplot2", dependencies = TRUE)
Warning in install.packages("ggplot2", dependencies = TRUE) :
  argument 'lib' is missing: using '/home/tiger/R/i486-pc-linux-gnu-library/2.11'
Warning: unable to access index for repository http://cran.cnr.Berkeley.edu/src/contrib
Warning message:
In getDependencies(pkgs, dependencies, available, lib) :
  package ‘ggplot2’ is not available
请问，如何解决？