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C # tutorial
Variables are containers for storing data values
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:
name <- "John"
age <- 40
name # output "John"
age # output 40
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.
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:
name <- "John Doe"
name # auto-print the value of the name 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.
name <- "John Doe"
print(name) # print the value of the name variable
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):
for (x in 1:10) {
print(x)
}
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.
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 (,
):
text <- "awesome"
paste("R is", text)
You can also use ,
to add a variable to another variable:
text1 <- "R is"
text2 <- "awesome"
paste(text1,
text2)
For numbers, the +
character works as a mathematical operator:
num1 <- 5
num2 <- 10
num1 + num2
If you try to combine a string (text) and a number, R will give you an error:
num <- 5
text <- "Some text"
num + text
Result:
Error in num + text : non-numeric argument to binary operator
R allows you to assign the same value to multiple variables in one line:
# Assign the same value to multiple variables in one line
var1 <- var2 <-
var3 <- "Orange"
# Print variable values
var1
var2
var3
# 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!