R Variables
Creating Variables in R
Variables are containers for storing data values.
R does not have a command for declaring a variable. A variable is created the moment you first assign a value to it. To assign a value to a variable, use the <-
sign. To output (or print) the variable value, just type the variable name:
From the example above, name and
age are variables, while
"John" and 40 are values.
In other programming language, it is common to use = as an assignment operator. In R, we can use
both = and <- as assignment operators.
However, <- is preferred in most cases because the = operator can be forbidden in some context in R.
Print / Output Variables
Compared to many other programming languages, you do not have to use a function to print/output variables in R. You can just type the name of the variable:
However, R does have a print() function
available if you want to use it. This might be useful if you are familiar with other programming languages, such as Python, which
often use a print() function to output variables.
And there are times you must use the print() function to output code, for example when working with for
loops (which you will learn more about in a later chapter):
Conclusion: It is up to your if you want to use the print()
function or not to output code. However, when your code is inside an R expression (for example inside curly braces
{} like in the example above), use the print() function if you want to output the result.
Concatenate Elements
You can also concatenate, or join, two or more elements, by using the paste() function.
To combine both text and a variable, R uses comma (,):
You can also use , to add a variable to another variable:
For numbers, the + character works as a mathematical operator:
If you try to combine a string (text) and a number, R will give you an error:
Example
num <- 5
text <- "Some text"
num + text
Result:
Error in num + text : non-numeric argument to binary operator
Multiple Variables
R allows you to assign the same value to multiple variables in one line:
Example
# Assign the same value to multiple variables in one line
var1 <- var2 <-
var3 <- "Orange"
# Print variable values
var1
var2
var3
Try it Yourself »
Variable Names
A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume). Rules for R variables are:- A variable name must start with a letter and can be a combination of
letters, digits, period(.)
and underscore(_). If it starts with period(.), it cannot be followed by a digit. - A variable name cannot start with a number or underscore (_)
- Variable names are case-sensitive (age, Age and AGE are three different variables)
- Reserved words cannot be used as variables (TRUE, FALSE, NULL, if...)
# Legal variable names:
myvar <- "John"
my_var <- "John"
myVar
<- "John"
MYVAR <- "John"
myvar2 <- "John"
.myvar <- "John"
# Illegal variable names:
2myvar <- "John"
my-var <- "John"
my var <- "John"
_my_var <- "John"
my_v@ar <- "John"
TRUE <- "John"
Remember that variable names are case-sensitive!
