Pandas cut() Function: Binning and Grouping Data (With Examples)

Data manipulation and analysis are essential tasks in the field of data science and analysis. One common requirement in data analysis is to categorize or bin numerical data into discrete intervals or groups. Pandas, a popular Python library for data manipulation and analysis, provides a powerful function called cut() that allows you to perform this task with ease. In this tutorial, we will explore the cut() function in detail, accompanied by practical examples to help you understand its usage effectively.

Table of Contents

1. Introduction to cut()
2. Syntax of cut()
3. Parameters of cut()
4. Creating Bins
5. Applying cut() to Categorize Data
6. Working with Labels
7. Handling Out-of-Bounds Values
8. Customizing Bin Intervals
9. Example 1: Age Binning
10. Example 2: Exam Score Classification
11. Conclusion

1. Introduction to cut()

The cut() function in Pandas is primarily used for binning and categorizing continuous data into discrete intervals. This process is often referred to as “binning” or “bucketing.” Binning data allows you to gain insights from continuous values by grouping them into meaningful categories. These categories or bins can be useful for generating summaries, visualizations, and further analysis.

2. Syntax of cut()

The basic syntax of the cut() function is as follows:

pandas.cut(x, bins, right=True, labels=None, retbins=False, precision=3, include_lowest=False, duplicates='raise')

Let’s break down the parameters of the cut() function:

• x: The input data (usually a Pandas Series or DataFrame column) that you want to categorize.
• bins: Either an integer specifying the number of equal-width bins to create, or a list of bin edges.
• right: A boolean indicating whether the bins should be right-closed (includes the right bin edge) or left-closed (includes the left bin edge).
• labels: An optional list or array of labels to assign to the resulting bins. If not provided, integer labels will be used.
• retbins: A boolean indicating whether to return the bin edges.
• precision: An integer specifying the decimal precision to round bin edges.
• include_lowest: A boolean indicating whether the left edge of the first bin should be included.
• duplicates: How to handle duplicate bin edges if encountered.

3. Parameters of cut()

Before we delve into examples, let’s explore the parameters of the cut() function in more detail.

• x: The input data to be binned. This can be a Pandas Series or DataFrame column containing continuous numerical data.
• bins: This parameter defines how the data will be grouped into bins. It can be specified in the following ways:
• An integer: This specifies the number of equal-width bins to create.
• A list or array of bin edges: This allows you to define custom bin edges. The data will be grouped between consecutive bin edges.
• right: This parameter determines whether the bins are right-closed or left-closed. If set to True (default), the bins are right-closed, meaning the right bin edge is included in the bin. If set to False, the bins are left-closed, meaning the left bin edge is included.
• labels: This parameter specifies the labels to assign to the resulting bins. If not provided, integer labels will be used. The number of labels should match the number of bins.
• retbins: If set to True, this parameter returns the bin edges along with the binned data. This can be useful if you want to further analyze or visualize the bin edges.
• precision: This parameter allows you to specify the decimal precision to round bin edges. The default precision is 3.
• include_lowest: If set to True, the left edge of the first bin will be included. This is useful when you have data points exactly on the lower bin edge.
• duplicates: This parameter determines how duplicate bin edges are handled. It can take the following values:
• 'raise' (default): Raises an error if duplicate bin edges are encountered.
• 'drop': Drops the duplicate bin edges and continues with the remaining unique bin edges.
• 'raise': Raises an error if duplicate bin edges are encountered.

4. Creating Bins

Before we proceed with examples, let’s understand the concept of creating bins. Bins are essentially the intervals into which you want to group your data. There are various strategies for defining bin edges, such as equal-width binning and custom binning.

Equal-Width Binning

Equal-width binning divides the range of data values into bins of equal width. This can be useful when you want to divide data into uniform intervals, regardless of the data distribution. For instance, if you’re categorizing ages, you might choose bins like 0-10, 11-20, 21-30, and so on.

Custom Binning

Custom binning allows you to define your own bin edges based on domain knowledge or specific requirements. This is particularly useful when the data distribution is not uniform and you want to group data based on meaningful cutoff points. For example, when categorizing exam scores, you might define custom bins like “Fail,” “Pass,” “Good,” and “Excellent.”

5. Applying cut() to Categorize Data

Now that we have a good understanding of the parameters and binning strategies, let’s walk through a basic example of how to use the cut() function to categorize data. In this example, we’ll use the cut() function to categorize a set of exam scores into letter grades.

import pandas as pd

# Sample data: Exam scores
exam_scores = [75, 90, 60, 82, 45, 92, 78, 88, 62, 70]

# Define bin edges for letter grades
grade_bins = [0, 59, 69, 79, 89, 100]

# Apply cut() to categorize the exam scores
grades = pd.cut(exam_scores, bins=grade_bins, labels=["F", "D", "C", "B", "A"])

# Print the categorized grades
print(grades)

In this example, we first import the Pandas library and create a list of exam scores. We then define the grade_bins list to specify the bin edges for different letter grades. The cut() function is applied to the exam_scores data using the specified grade_bins and corresponding labels. The resulting grades variable contains the categorized grades for each exam score.

6. Working with Labels

The labels parameter of the cut() function allows you to assign custom labels to the resulting bins. If you do not provide labels, integer labels will be automatically assigned to the bins. Let’s see how you can customize labels using the same example as before:

import pandas as pd

# Sample data: Exam scores
exam_scores = [

75, 90, 60, 82, 45, 92, 78, 88, 62, 70]

# Define bin edges for letter grades
grade_bins = [0, 59, 69, 79, 89, 100]

# Custom labels for letter grades
grade_labels = ["Failing", "Below Average", "Average", "Above Average", "Excellent"]

# Apply cut() with custom labels
custom_grades = pd.cut(exam_scores, bins=grade_bins, labels=grade_labels)

# Print the categorized grades with custom labels
print(custom_grades)

In this example, we’ve defined custom labels using the grade_labels list. When we apply the cut() function with these custom labels, the resulting custom_grades variable contains the categorized grades with the specified labels.

7. Handling Out-of-Bounds Values

When using the cut() function, it’s important to consider how out-of-bounds values are handled. Out-of-bounds values are data points that fall outside the specified bin edges. By default, cut() will raise an error if it encounters out-of-bounds values. However, you can control this behavior using the include_lowest parameter.

The include_lowest parameter, when set to True, includes the left edge of the first bin. This means that the lowest bin edge is treated as an inclusive bound. Let’s illustrate this with an example:

import pandas as pd

# Sample data: Temperatures in Celsius
temperatures = [-5, 10, 20, 30, 40]

# Define bin edges for temperature ranges
temp_bins = [0, 10, 20, 30]

# Apply cut() with include_lowest=True
temp_categories = pd.cut(temperatures, bins=temp_bins, include_lowest=True)

# Print the categorized temperature ranges
print(temp_categories)

In this example, the temperatures include values below the first bin edge (-5) and above the last bin edge (40). By setting include_lowest=True, the first bin is inclusive of the left edge. This results in the first temperature being categorized in the range of [0, 10).

8. Customizing Bin Intervals

Customizing bin intervals allows you to define specific cutoff points for your data. You can achieve this by providing a list of bin edges to the bins parameter. This approach is particularly useful when you want to create bins based on domain knowledge or specific requirements.

Let’s consider an example where we categorize ages into different life stages:

import pandas as pd

# Sample data: Ages
ages = [18, 25, 30, 42, 50, 60, 75]

# Define custom bin edges for life stages
age_bins = [0, 18, 30, 50, 100]

# Apply cut() to categorize ages into life stages
life_stages = pd.cut(ages, bins=age_bins, labels=["Child", "Young Adult", "Middle-Aged", "Senior"])

# Print the categorized life stages
print(life_stages)

In this example, we’ve defined custom bin edges using the age_bins list. The cut() function is then applied to categorize ages into different life stages using the specified bin edges and labels.

9. Example 1: Age Binning

Let’s now explore a more detailed example to further demonstrate the practical use of the cut() function. In this example, we’ll work with a dataset containing ages and categorize them into different age groups.

import pandas as pd

# Sample data: Ages
ages = [22, 15, 30, 45, 12, 60, 34, 29, 18, 50, 8, 67]

# Define bin edges for age groups
age_bins = [0, 18, 35, 50, 100]

# Apply cut() to categorize ages into age groups
age_groups = pd.cut(ages, bins=age_bins, labels=["Under 18", "18-34", "35-50", "Over 50"])

# Create a DataFrame to display results
result_df = pd.DataFrame({"Age": ages, "Age Group": age_groups})

# Print the categorized age groups
print(result_df)

In this example, we start by importing Pandas and defining the ages list. We then define age_bins to categorize ages into different groups. The cut() function is used to categorize ages based on the specified bin edges and labels. The resulting result_df DataFrame displays the original ages alongside their respective age groups.

10. Example 2: Exam Score Classification

Let’s explore another example involving exam scores, where we’ll use the cut() function to classify scores into different performance categories.

import pandas as pd

# Sample data: Exam scores
exam_scores = [75, 90, 60, 82, 45, 92, 78, 88, 62, 70]

# Define bin edges for score classification
score_bins = [0, 60, 70, 80, 90, 100]

# Custom labels for score categories
score_labels = ["Failing", "D", "C", "B", "A"]

# Apply cut() with custom labels
score_categories = pd.cut(exam_scores, bins=score_bins, labels=score_labels)

# Create a DataFrame to display results
score_result_df = pd.DataFrame({"Score": exam_scores, "Category": score_categories})

# Print the categorized score categories
print(score_result_df)

In this example, we import Pandas and define the exam_scores list. We then set up score_bins to categorize the scores into different performance categories. Custom labels are defined using the score_labels list. The cut() function is applied with the specified bins and labels, and the resulting score_result_df DataFrame displays the original scores along with their corresponding categories.

11. Conclusion

The cut() function in Pandas is a versatile tool for binning and categorizing continuous data into discrete intervals. It allows you to group data based on predefined bin edges and customize labels for the resulting bins. By effectively using the cut() function, you can gain insights from your data by categorizing it into meaningful groups, facilitating better analysis and visualization. Through the examples presented in this tutorial, you’ve learned how to apply the cut() function to various scenarios, such as age binning and exam score classification. As you continue to work with data, the ability to categorize and group data using cut() will undoubtedly prove valuable in your data analysis journey.