You can use the unlist() function in R to quickly convert a list to a vector.

This function uses the following basic syntax:

unlist(x)

where:

• x: The name of an R object

The following examples show how to use this function in different scenarios.

Example 1: Use unlist() to Convert List to Vector

Suppose we have the following list in R:

#create list
my_list <- list(A = c(1, 2, 3),
                B = c(4, 5),
                C = 6)

#display list
my_list

$A
[1] 1 2 3

$B
[1] 4 5

$C
[1] 6

The following code shows how to convert a list to a vector using the unlist() function:

#convert list to vector
new_vector <- unlist(my_list)

#display vector
new_vector

A1 A2 A3 B1 B2  C 
 1  2  3  4  5  6 

Note that you can specify use.names = FALSE to remove the names from the vector:

#convert list to vector
new_vector <- unlist(my_list, use.names = FALSE)

#display vector
new_vector

[1] 1 2 3 4 5 6

Example 2: Use unlist() to Convert List to Matrix

The following code shows how to use unlist() to convert a list to a matrix:

#create list
my_list <- list(1:3, 4:6, 7:9, 10:12, 13:15)

#convert list to matrix
matrix(unlist(my_list), ncol=3, byrow=TRUE)

     [,1] [,2] [,3]
[1,]    1    2    3
[2,]    4    5    6
[3,]    7    8    9
[4,]   10   11   12
[5,]   13   14   15

The result is a matrix with five rows and three columns.

Example 3: Use unlist() to Sort Values in List

Suppose we have the following list in R:

#create list
some_list <- list(c(4, 3, 7), 2, c(5, 12, 19)) 

#view list
some_list

[[1]]
[1] 4 3 7

[[2]]
[1] 2

[[3]]
[1]  5 12 19

Now suppose we attempt to sort the values in the list:

#attempt to sort the values in the list
sort(some_list)

Error in sort.int(x, na.last = na.last, decreasing = decreasing, ...) : 
  'x' must be atomic

We receive an error because the list must first be converted to a vector for us to sort the values.

We can use the following unlist() function to sort the values:

#sort values in list
sort(unlist(some_list))

[1]  2  3  4  5  7 12 19

Notice that we’re able to successfully sort the list of values without any error because we first used unlist(), which converted the list to a numeric vector.

Additional Resources