Variables in R

Variables in R are the same as the notion of variables in any other programming language. Variable is a name we assign for the storage space location that stores our data. A variable in R can be of any datatype, simple or complex. There are certain rules and conventions when working with variables in R.

Variables in R – Naming Rules

The name of a variable is known as an identifier. Not every string can be an identifier in R.

• Variables in R are case sensitive. The names Car, car and CAR are all treated as different variables in spite of the same spelling.
  
  
• Variables can never begin with symbols or numbers. 1car and &car are not valid variable names.
  
  
• Variable names can begin with a period (.). However, if a name starts with a period, it must be followed by a letter instead of a number.
  
  
• For defining complex names, period or underscore can be used as the seperator. For example, a.one and a_one are both valid variable names.
  
  
• However, since underscore was used as an assignment operator in earlier versions of R, a period is preferred over underscore.
  
  
• Variable names can never contain a blank space.

Variable Assignment

In the previous post on data types in R, we have introduced the assignment operator in R <-. This is knows as the gets operator. When we write a statement a <- b, it can be verbally expressed as, a gets the value of b.

Never put a space between the less than and hyphen in our gets operator. The statement a <- 10 is an assignment statement, whereas a < -10 is interpreted as a less than minus 10, resulting in a Boolean output.

In addition to the gets operator, there is also the right assignment operator, that is a reverse of gets ->. The statement 10 -> a is equivalent to a <- 10.

Also, the equals sign can be used for assignment of variables in R just like C or C++. The statement a = b is a valid one.

Some Useful Tips with Variables

• When working with complex projects, it sometimes gets tedious to remember all the variable names. Therefore you can type in ls() in the console to get a list of all active variables.
• To remove a specific variable from the environment the command is rm(<variablename>). The space gets freed and can be reassigned to another variable now. To remove a variable named x, simply type in rm(x).
• The code snippet below displays the ls() utility. All the variables and function names in the enivornment get displayed.

> ls()
 [1] "a"          "a_one"      "average"    "b"          "c"          "code"      
 [7] "division"   "elfunction" "fs"         "myname"     "myname2"    "myvector"  
[13] "name

• Suppose that we need to remove a variable named average, it can be done by typing in rm(average) . Using ls again, we see that the variable in no longer in the environment.

> rm(average)
> ls()
 [1] "a"          "a_one"      "b"          "c"          "code"       "division"  
 [7] "elfunction" "fs"         "myname"     "myname2"    "myvector"   "name"