unique Function in R (2 Examples)


On this page you’ll learn how to remove duplicates from vectors and data frames using the unique function in R.

The article contains this information:

Here’s the step-by-step process.

Definition & Basic R Syntax of unique Function


Definition: The unique R function removes duplicates from data objects.


Basic R Syntax: Please find the basic R programming syntax of the unique function below.

unique(x)                                          # Basic R syntax of unique function


I’ll show in the following two examples how to use the unique function in R programming. So keep on reading…

Example 1: Return Unique Elements of Vector

Example 1 illustrates how to retain only unique elements of a vector using the unique() function in R. First, we have to create an exemplifying vector:

vec <- c(1, 3, 3, 1, 4, 7, 1)                      # Create example vector
vec                                                # Print example vector
# 1 3 3 1 4 7 1

Our example vector contains seven numeric elements.

Now, we can apply the unique command as shown below:

vec_unique <- unique(vec)                          # Apply unique() to vector
vec_unique                                         # Print updated vector
# 1 3 4 7

As you can see based on the output of the RStudio console, the unique function extracted only four elements of our original input vector. In other words: three of the vector elements were duplicates.


Example 2: Return Unique Rows of Data Frame

In this Example, I’ll illustrate how to use the unique function to remove duplicate rows of a data matrix. Again, let’s create some example data:

data <- data.frame(x1 = c(1, 1, 2, 3, 4, 2, 2),    # Create example data
                   x2 = c("a", "a", "a", "b", "c", "c", "a"))
data                                               # Print example data
#   x1 x2
# 1  1  a
# 2  1  a
# 3  2  a
# 4  3  b
# 5  4  c
# 6  2  c
# 7  2  a

Our data table consists of seven rows and two columns. The variable x1 is numeric and the variable x2 is a character string.

Now, let’s apply the unique function to these data:

data_unique <- unique(data)                        # Apply unique() to data frame
data_unique                                        # Print updated data frame
#   x1 x2
# 1  1  a
# 3  2  a
# 4  3  b
# 5  4  c
# 6  2  c

The RStudio console returns only five out of the original seven lines of data. The second and seventh rows were removed.


Video, Further Resources & Summary

Would you like to learn more about the application of the unique function? Then I can recommend to watch the following video of my YouTube channel. In the video, I’m explaining the R codes of this post in RStudio:



In addition, I can recommend to have a look at the other articles of this website.


To summarize: This article showed how to apply the unique function in R programming. If you have any additional comments and/or questions, let me know in the comments section below.


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