A dataframe in R is a data structure used to store tabular data in rows and columns. In this tutorial, we will look at how to count the unique values in a column of an R dataframe with the help of some examples.

## How do you get the unique values count of an R dataframe column?

You can use a combination of the `length()`

function and the `unique()`

function in R to get the count of unique values in a dataframe column.

The idea is to first get the unique values from the column in a vector using the `unique()`

function and then apply `length()`

function on this unique values vector to get a count of the unique values in the column.

The following is the syntax –

length(unique(dataframe[[columan_name]]))

We get the unique values count in the column as an integer.

## Steps to count distinct values in an R dataframe column

Let’s now look at the steps to follow to get distinct values in a dataframe column in R

### Step 1 – Create a dataframe

First, we will create a dataframe that we will be using throughout this tutorial.

# create a dataframe employees_df = data.frame( "Name"= c("Jim", "Dwight", "Angela", "Tobi", "Kevin"), "Age"= c(26, 28, 29, 32, 30), "Department"= c("Sales", "Sales", "Accounting", "HR", "Accounting") ) # display the dataframe print(employees_df)

Output:

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Name Age Department 1 Jim 26 Sales 2 Dwight 28 Sales 3 Angela 29 Accounting 4 Tobi 32 HR 5 Kevin 30 Accounting

We now have a dataframe containing information about some employees working in an office. The dataframe has columns “Name”, “Age”, and “Department”.

### Step 2 – Get the count of the unique values in the column using `unique()`

and `length()`

To get the unique value count in a column, pass the column values vector to the `unique()`

function as an argument. You can use the `[[]]`

notation to get a column’s values vector. This will result in a vector of unique values from the column.

Then, you can then apply the `length()`

function on this vector of unique values to get the unique values count.

Let’s get the count of distinct departments from the “Department” column in the above dataframe.

# get count of distinct values in "Department" column dept_count <- length(unique(employees_df[["Department"]])) # display the result print(dept_count)

Output:

[1] 3

We get the number of unique values in the “Department” column as 3.

Note that you can also use the column index to access a column’s values. For example, in the above dataframe, the index of the “Department” column is 3 (rows and columns in R are indexed starting from 1).

# get count of distinct values in "Department" column dept_count <- length(unique(employees_df[[3]])) # display the result print(dept_count)

Output:

[1] 3

We get the same result as above.

## Summary

In this tutorial, we looked at how to count the unique values in the column in an R dataframe. The following is a short summary of the steps –

- Create a dataframe (skip this step if you already have a dataframe on which you want to operate).
- Use a combination of the
`unique()`

and the`length()`

functions in R to count the unique values in a column.

You might also be interested in –

- Create a DataFrame in R
- How to Add a Row to a Dataframe in R?
- How to Add a Column to a Dataframe in R?

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