split & unsplit Functions in R (2 Examples)

In this R tutorial you’ll learn how to divide (and reassemble) vectors into groups using the split function.

The tutorial is structured as follows:

Let’s dig in:

Definitions & Basic R Syntaxes of split and unsplit Functions

Definitions: Please find the definitions of the split and unsplit functions below.

• The split R function divides data into groups.
• The unsplit R function reverses the output of the split function.

Basic R Syntaxes: You can find the basic R programming syntaxes of the split and unsplit functions below.

split(values, groups)                      # Basic R syntax of split function
unsplit(split_values, groups)              # Basic R syntax of unsplit function

I’ll illustrate in the following two examples how to apply the split and unsplit functions in the R programming language.

Creation of Example Data

First, we’ll need to create some data that we can use in the example code below:

vec <- 1:10                                # Create example vector
vec                                        # Print example vector
# 1  2  3  4  5  6  7  8  9 10

Have a look at the previous output of the RStudio console. It shows that our example data is a simple numeric vector ranging from 1 to 10.

For the application of the split and unsplit commands, we also have to create a grouping vector:

groups <- c(rep("A", 3),                   # Create grouping vector
            rep("B", 5),
            rep("C", 2))
groups                                     # Print grouping vector
# "A" "A" "A" "B" "B" "B" "B" "B" "C" "C"

Our grouping vector contains of ten elements that are separating our data into three groups A, B, and C.

Example 1: Using split() Function in R

This Example explains how to divide our example data using the split function in R. Have a look at the following programming syntax and its output:

my_split <- split(vec, groups)             # Apply split function
my_split                                   # Print output
# $A
# [1] 1 2 3
# 
# $B
# [1] 4 5 6 7 8
# 
# $C
# [1]  9 10

As you can see, the previous R code created a list called my_split, which contains three list elements. Each list elements consists of the values that correspond to the groups A, B, and C.

Example 2: Using unsplit() Function in R

It is also possible to reverse the output of the split function using unsplit. In Example 2, I’ll show how to do that:

my_unsplit <- unsplit(my_split, groups)    # Apply unsplit function
my_unsplit                                 # Print output
# 1  2  3  4  5  6  7  8  9 10

As you can see, the previous output is exactly the same as our original vector. In other words: the output of the split function was reversed.

Video & Further Resources

In case you need further information on the R code of this article, I can recommend to watch the following video which I have published on my YouTube channel. In the video, I’m explaining the R codes of this article:

In addition to the video, you might read the related articles of my website:

• Split Data Frame in R
• Split Data Frame into List of Data Frames Based On ID Column
• Split Data Frame Variable into Multiple Columns
• str_split & str_split_fixed Functions
• R Functions List (+ Examples)
• The R Programming Language

This page showed how to apply the split and unsplit functions in the R programming language. Tell me about it in the comments section, if you have any further questions.