R unlist Function | 3 Example Codes (List of Vectors, Data Frame & String)

Basic R Syntax:

unlist(my_list)

The unlist R function converts a list to a single vector. The basic code for unlist in R is illustrated above.

In the following tutorial, I will show you several examples for the application of the unlist function in R. Let’s dive in…

Example 1: Unlist List of Vectors in R

Let’s begin with a simple example: The conversion of a list of numeric vectors into a single vector. Consider the following example list:

my_list <- list(l1 = c(1, 7, 3, 5),                 # First list element
                l2 = c(5, 3, 9),                    # Second list element
                l3 = c(9, 9, 22, 5, 17, 83, 105))   # Third list element
my_list

Example List for the Application of the R unlist Function

Graphic 1: Example List for the Application of unlist in R.

Our example list consists of three elements. Each of them is a numeric vector.

Now, let’s apply the unlist R function:

unlist(my_list)                                     # Apply unlist R function
# l11 l12 l13 l14 l21 l22 l23 l31 l32 l33 l34 l35 l36 l37 
#   1   7   3   5   5   3   9   9   9  22   5  17  83 105

As you can see based on this unlist R example, the function returns a vector consisting of all values of the three vectors within my_list.

Additionally, each value of the output vector is named with the list name + an indicator for the position of each value within the original list element. For instance, the value 7 appears in the first list element l1 at the second position. For that reason, in the output vector its name is l12 (i.e. l1 + 2).

If you want to get rid of these names, you can simply add the specification use.names = FALSE within the unlist R function:

unlist(my_list, use.names = FALSE)                  # Apply unlist without names
#   1   7   3   5   5   3   9   9   9  22   5  17  83 105

Check out the following video of my YouTube channel. The video explains the R programming syntax of Example 1 in more detail:

Example 2: Unlist a List with Data Frames

The unlist function can also be applied to a list that includes a data frame. Consider the following modified example list:

my_list_2 <- my_list                                # Create modified list
my_list_2[[4]] <- data.frame(x1 = c(5, 1, 2),       # Add a data frame to the list
                             x2 = c(7, 5, 7))

To such a list with dataframes, we can also apply the unlist command:

unlist(my_list_2)                                   # Unlist list with data.frame
# l11 l12 l13 l14 l21 l22 l23 l31 l32 l33 l34 l35 l36 l37 x11 x12 x13 x21 x22 x23 
#   1   7   3   5   5   3   9   9   9  22   5  17  83 105   5   1   2   7   5   7

As you can see, each column of the data matrix is unlisted itself.

Example 3: Unlist a String in R

It is even possible to unlist a string (i.e. a data object of character class). First, let’s modify our list once more:

my_list_3 <- my_list_2                              # Create modified list
my_list_3[[5]] <- c("A", "Y", "H")                  # Add string element to list

Our new list, my_list_3, consists of three numeric vectors, one data table of the class data.frame, and one character vector.

Now, let’s apply the unlist command to this list:

unlist(my_list_3)                                   # Unlist string in R
# l11   l12   l13   l14   l21   l22   l23   l31   l32   l33   l34   l35   l36   l37 
# "1"   "7"   "3"   "5"   "5"   "3"   "9"   "9"   "9"  "22"   "5"  "17"  "83" "105" 
# x11   x12   x13   x21   x22   x23                   
# "5"   "1"   "2"   "7"   "5"   "7"   "A"   "Y"   "H"

No problem – Everything is converted into one single vector. However, note that all values of the output vector are converted to the character class!