Getting Started with R

R is a programming language for statistical computing, data manipulation, and graphical display. R is a highly extensible language and has become a popular language for Data Analytics. The R software can be downloaded from https://cran.r-project.org

Topics covered in this section are

  ➤ Getting Help

  ➤ Installed Packages and Objects

  ➤ In-built Data Sets

  ➤ Executing in-built examples

  ➤ Saving, loading, and removing R data structures

Getting Started with R

↪ Getting Help

The help() function or '?' operator can be used for finding help for objects, functions, and data sets.

      help()                       # Shows help documentation      
      help("read.table")           # help for read.table() function
      ?read.csv                    # help for read.csv() function
      help(package="MASS")         # help for package MASS. 
      help(lm.gls, package="MASS") # help for function lm.gls() under package MASS
      help(package=curl)           # help for package mass. Note: double quote is optional

The help.search() function searches the documentation for packages installed. The search can be based on pattern matching.

      help.search("list")
      help.search("^lm")           # search can be based on pattern matching

The ?? operator is a synonym for help.search() function.

      ??list
      ??"^Date"
      ??read.table

Getting Started with R

↪ Getting Help

The help.start() starts the HTML version of R’s documentation.

      help.start()
      help.start("list")

Packages may include vignettes, which are meant to illustrate and explain facilities in the R package. The browseVignettes() function displays vignettes from installed packages in the browser.

      browseVignettes()  
      browseVignettes(package="glue")  # Vignettes in package glue displayed in the browser

The vignette() function displays a list of vignettes in text form.

      vignette()
      vignette(package="glue")   # Vignettes in package glue displayed in the browser

Getting Started with R

↪ Installed Packages and Objects

The installed.packages() function lists installed packages in R.

      installed.packages()

The above function lists all the details of installed packages. The first column display package names.

      installed.packages()[,1]     # Display first column of the installed packages

The objects() and ls() functions can be used for listing the names of the objects, data sets, and functions available or defined in the workspace. The data is not displayed when there is no data in the workspace.

      objects()               # Lists all objects available in the current workspace
      ls()                    # Same as objects()
      objects(pattern = "d")  # Display the objects that has 'd' in it

The apropos() function searches objects and functions, directly accessible in the current R session. The apropos(“^lm”) returns the names of all accessible objects that start with the character “lm”.

      apropos("^lm")

The library() function display all available packages in the libraries specified by lib.loc – a character vector describing the location of R library trees to search through.

      help(library)
      library()

Getting Started with R

↪ In-built Data Sets

There are example data sets available within R along with loaded packages. The library(MASS) loads the package MASS (for Modern Applied Statistics with S) into memory. The data() function will list all the data sets in the loaded packages. The data(Animals) will load the data set Animals into memory. Then type Animals to display the data available in the Animals data set.

      library(MASS)
      data()
      data(Animals)
      Animals
      help(Animals, package="MASS")  # Get the help on Animals data set

The typeof() function determines the R internal type or storage mode of any object, and the class() function checks the data type.

      typeof(Animals)    # Display [1] "list"
      class(Animals)     # Display [1] "data.frame"

The data() function loads the data set into the memory.

      data("Animals")     # loads the data set Animals into memory
      Animals
      Animals$body        # Prints contents of column "body"
      class(Animals$body) # Display [1] "numeric"

The attach() function attaches a set of R objects to the search path. The above Animals$body call can be simplified using attach().

      attach(Animals)      # Attaches Animals data set to search path
      body                 # Same as Animals$body call

The function detach() removes the data set from the search path.

      detach(Animals) 
      body                 # Display error

Getting Started with R

↪ Executing in-built examples

Help pages for functions generally include executable examples demonstrating how the functions work. The example() function can be used for executing the examples in help pages.

      example("list")         # Executes examples from list help page      
      example(read.table)     # Executes examples from read.table help page

Packages may also include demos. The demo() function lists all demos for all installed packages

      demo()               # Lists demos from installed packages
      demo(recursion)      # Executes demos from recursion package

Getting Started with R

↪ Saving, loading, and removing R data structures

The ls() and rm() functions show and remove objects from memory.

      ls()         # Show all the objects in memory
      dframe       # Display dframe object if present
      rm(m, z)     # Removes m and z objects if present
      ls()

The rm() function with list=ls() argument removes all objects or clear the entire R session.

      rm(list=ls())

The save() function saves objects into a file.

      save(m, z, x, file = "mydata.Rdata")

The load() function loads the file and recreates the data structure.

      load("mydata.Rdata")

The save.image() function saves the R session into the .Rdata file.

      save.image()

The q() function can be used for quitting the R session.

      q()

Getting Started with R

↪ Summary