duplicated() function in R: Find duplicated elements in a vector or dataframe

duplicated()

rstats

In this tutorial, we will learn about the base R function duplicated() and how can we use duplicated() function to find if an element in a vector is duplicat…

Published

June 30, 2021

Find Duplicate elements in a vector with duplicated()

Let us create some data vector with duplicates. Here we use sample() function to get bootstrapped samples with replacements.

set.seed(123)
x  
##  1     3     2
##  2     3     2
##  3     3     1
##  4     2     2
##  5     3     3
##  6     2     1
##  7     2     3
##  8     2     3
##  9     3     1
## 10     1     1

By using duplicated() function on the dataframe we can get boolean vector identifying if the row is duplicated or not.

duplicated(df)
##  [1] FALSE  TRUE FALSE FALSE FALSE FALSE FALSE  TRUE  TRUE FALSE

In this example, we can see that second row is duplicated and eighth row is also duplicated as they are TRUE in the boolean vector.

Find Duplicated rows in a matrix with duplicated()

We can use duplicated() function on a matrix to find the rows that are duplicated. Let us convert the dataframe we created above into a matrix using as.matrix() function.

mat <- as.matrix(df)

Now we have our data as matrix and using duplicated() function on the matrix, we can identify the rows that are duplicated.

duplicated(mat)
##  [1] FALSE  TRUE FALSE FALSE FALSE FALSE FALSE  TRUE  TRUE FALSE

---
title: "duplicated() function in R: Find duplicated elements in a vector or dataframe"
description: "In this tutorial, we will learn about the base R function duplicated() and how can we use duplicated() function to find if an element in a vector is duplicat..."
date: 2021-06-30
categories: ['duplicated()', 'rstats']
format:
  html:
    code-fold: false
    code-tools: true
---

###  Find Duplicate elements in a vector with duplicated()
Let us create some data vector  with duplicates. Here [we use sample() function to get bootstrapped samples](https://rstats101.com/sample-function-in-r/) with replacements.

```r
set.seed(123)
x  
##  1     3     2
##  2     3     2
##  3     3     1
##  4     2     2
##  5     3     3
##  6     2     1
##  7     2     3
##  8     2     3
##  9     3     1
## 10     1     1
```

By using duplicated() function on the dataframe we can get boolean vector identifying if the row is duplicated or not.
```r
duplicated(df)
##  [1] FALSE  TRUE FALSE FALSE FALSE FALSE FALSE  TRUE  TRUE FALSE
```
In this example, we can see that second row is duplicated and eighth row is also duplicated as they are TRUE in the boolean vector.

###  Find Duplicated rows in a matrix with duplicated()

We can use duplicated() function on a matrix to find the rows that are duplicated. Let us convert the dataframe we created above [into a matrix using as.matrix() function](https://rstats101.com/3-useful-matrix-functions-in-r-matrix-is-matrix-and-as-matrix/).
```r
mat <- as.matrix(df)
```

Now we have our data as matrix and using duplicated() function on the matrix, we can identify the rows that are duplicated.  
```r
duplicated(mat)
##  [1] FALSE  TRUE FALSE FALSE FALSE FALSE FALSE  TRUE  TRUE FALSE
```

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