Create variables through assignments

May 5, 2020
By

[This article was first published on Quantargo Blog, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)
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Usually you want to store vectors and other objects into variables so you can work with them more easily. Variables are like a box with a name. You can then refer to the name to see what is stored inside.

  • Learn how to create a variable
  • Use variables to store objects and vectors
  • Reuse assigned objects through a variable name
___ <- ___

Assigning variables

Usually you want to use objects like vectors more than once. In order to save the trouble of retyping and recreating them all the time, we would like to save them somewhere and reuse them later.

To do this, we can assign them to a variable name. R uses the special arrow operator <- for assigning values to a variable. The arrow is simply the combination of a smaller-than character (<) and a minus sign (-).

Let’s take a look at an example, in which we assign a numeric vector to a variable named numbers:

numbers <- c(1, 2, 3, 4, 5, 6, 7, 8, 9)

Now we can use the variable’s name below to see its contents:

numbers
[1] 1 2 3 4 5 6 7 8 9

Note, that when we assign something to a variable that already exists, it gets overwritten. All previous contents are automatically removed:

numbers <- c(10, 11, 12, 13)
numbers
[1] 10 11 12 13

Once you have defined a variable, you can use it just like you would use the underlying vector itself. In the following example we create two numeric vectors and assign them to the variables low and high. Then, we use these variables and concatenate the two vectors into a single one and assign it to the variable named sequence. Finally we call the sequence variable and inspect its contents:

low <- c(1, 2, 3)
high <- c(4, 5, 6)
sequence <- c(low, high)
sequence
[1] 1 2 3 4 5 6

As you can see, the vectors 1, 2, 3 and 4, 5, 6 stored in the variables low and high, were combined into a single vector that is now the the content of the variable sequence.

Exercise: Assign numeric vector to variable

  • Use the concatenate function c() and create a vector containing the numbers 2, 3, 5 and 7.
  • Assign this vector to a variable named primes.

Start Exercise

Exercise: Assign character vector to variable

Use the concatenate function c() and create a vector containing the words

  • "programming"
  • "R" and
  • "variables"

Assign this vector to the variable fun.

Start Exercise

Quiz: Variable Overriding

fun <- c("programming", "in", "R") 
fun <- c("Have", "fun")
fun

Inspect the code chunk above. What is the content of the variable fun in the last step?

  • "programming" "in" "R"
  • "Have" "fun"
  • "programming" "in" "R" "Have" "fun"
  • There is no output, only an error message.

Start Quiz

Quiz: Vector Concatenation

fun <- c("programming", "in", "R") 
fun2 <- c("Have", "fun")
fun3 <- c(fun2, fun)
fun3

Inspect the code chunk above. What is the content of the variable fun3 in the last step?

  • "programming" "in" "R" "Have" "fun"
  • "Have" "fun"
  • "Have" "fun" "programming" "in" "R"
  • There is no output, only an error message.

Start Quiz

Naming rules

There are a few rules we need to consider when creating variables.

Variable rules

  • Can contain letters: example
  • Can contain numbers: example1
  • Can contain underscores: example_1
  • Can contain dots: example.1
  • Cannot start with numbers: 2example
  • Cannot start with underscores: _example
  • Cannot start with a dot if directly followed by a number: .2example

Quiz: Naming Rules

Which of the following variable names are valid?

  • weekly+tasks
  • task2Do
  • 24hour
  • .task

Start Quiz

Create variables through assignments is an excerpt from the course Introduction to R, which is available for free on quantargo.com

VIEW FULL COURSE

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