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Installing and Using an R Package

• An R package is a library that contains R functions and other R objects.
   
• Some packages ship with R and are loaded when R is invoked. Use the R search function to see which packages are currently loaded. With the version of R recommended for this course this is the output from the search function without loading any external packages:
  

  > search()
  [1] .GlobalEnv        package:stats     package:graphics 
  [4] package:grDevices package:utils     package:datasets 
  [7] package:methods   Autoloads         package:base      
  

  This shows that the packages stats, graphics, grDevices, utils, datasets, methods, and base are all preloaded when R is invoked.
   
• To install the R package leaps from the internet, use the install.packages function:
  

  > install.packages("leaps")
  

• To load the R package leaps after it has been installed, use the library function:
  

  > library(leaps)
  

• If you use the search function again, you can verify that the leaps package is now loaded:

  > search()
   [1] .GlobalEnv        package:leaps     package:stats    
   [4] package:graphics  package:grDevices package:utils    
   [7] package:datasets  package:methods   Autoloads        
  [10] package:base