# Transforming Data with the If Value in Column Then Formula in Pandas

## Using a Formula for If Value in Column Then in Pandas

When working with a Pandas DataFrame, it’s common to need to create a new column based on the values in an existing column. This is especially true if you need to perform some kind of computation or transformation on the values in the original column.

Fortunately, Pandas provides a simple and efficient way to do this using the “if value in column then” formula. This article will demonstrate how to use this formula to assign values to a column based on values in another column, and provide an example to illustrate this concept.

## Assigning values to a column based on values in another column

Before we dive into the formula itself, let’s examine what we’re trying to accomplish. Let’s say we have a DataFrame with a column called “income” that contains the income of a group of individuals.

We want to create a new column called “income class” that assigns a value of “low”, “medium”, or “high” based on the income of the person. To accomplish this, we can use the “if value in column then” formula in conjunction with the .loc function.

The “if value in column then” formula takes the following structure:

df.loc[criteria, ‘new_column_name’] = value

Here, “df” is the name of your DataFrame, “criteria” is a logical statement that defines under which conditions the new column should receive the desired value, “new_column_name” is the name you want to give your new column, and “value” is the value you want to assign to the new column based on your criteria.

For our example, let’s use the following criteria:

income <= 30000 --> ‘low’

income > 30000 and income <= 70000 --> ‘medium’

income > 70000 –> ‘high’

This assigns the ‘low’ income class to those with an income less than or equal to 30,000, the ‘medium’ income class to those with an income greater than 30,000 but less than or equal to 70,000, and ‘high’ income class to those with an income greater than 70,000.

To implement this formula, we can use the following code:

df.loc[df[‘income’] <= 30000, 'income class'] = 'low'

df.loc[(df[‘income’] > 30000) & (df[‘income’] <=70000), 'income class'] = 'medium'

df.loc[df[‘income’] > 70000, ‘income class’] = ‘high’

Let’s break this down. In the first line, we create a new column called ‘income class’ using the .loc function and assign the value ‘low’ to it for all rows that meet the criteria of having an income less than or equal to 30,000.

In the second line, we use & to specify that we want to select rows where the income is greater than 30,000 AND less than or equal to 70,000, and assign the value ‘medium’ to the ‘income class’ column for these rows using the .loc function. Finally, in the third line, we select rows where the income is greater than 70,000 and assign the value ‘high’ to the ‘income class’ column for these rows using the .loc function.

Example: Using a Formula for “If Value in Column Then” in Pandas

Let’s create a simple example to demonstrate how to use the “if value in column then” formula in Pandas. We’ll create a DataFrame that contains the name and age of a group of people, and we want to create a new column called “age group” that assigns a value of “young”, “middle-aged”, or “old” based on the age of the person.

To create the DataFrame, we can use the following code:

import pandas as pd

data = {‘Name’: [‘John’, ‘Tom’, ‘Kim’, ‘Mary’, ‘Peter’, ‘Alex’, ‘Mike’, ‘George’, ‘Jane’, ‘Liam’],

‘Age’: [18, 25, 35, 40, 50, 60, 70, 80, 90, 100]}

df = pd.DataFrame(data)

This creates a DataFrame with two columns, “Name” and “Age”, containing the name and age of ten individuals.

To create the “age group” column using the “if value in column then” formula, we can use the following code:

df.loc[df[‘Age’] < 30, 'Age Group'] = 'Young'

df.loc[(df[‘Age’] >= 30) & (df[‘Age’] <= 60), 'Age Group'] = 'Middle-Aged'

df.loc[df[‘Age’] > 60, ‘Age Group’] = ‘Old’

This creates a new column called “Age Group” and assigns values of “Young”, “Middle-Aged”, and “Old” based on the age of each individual.

The first line assigns the “Young” age group to those under 30, the second line assigns the “Middle-Aged” age group to those between 30 and 60 years old, and the third line assigns the “Old” age group to those over 60.

To learn more about working with Pandas and using the “if value in column then” formula, there are many excellent resources available. Some of our favorites include:

– Pandas documentation: This is the official documentation for Pandas and is a comprehensive resource for learning how to use the library.

It includes tutorials, examples, and references for all aspects of Pandas. – Pandas Cookbook: This free online resource provides a collection of Pandas recipes for common data manipulation tasks.

It includes step-by-step instructions and example code for each recipe. – Data Wrangling with Pandas: This online course from DataCamp provides a hands-on introduction to Pandas and covers topics like indexing, grouping, and merging data.

– Pandas User Guide: This free online guide provides an in-depth exploration of Pandas and covers topics like data structures, indexing, and data manipulation.

## Conclusion

In conclusion, if you’re working with a Pandas DataFrame and need to create a new column based on values in an existing column, the “if value in column then” formula can be a powerful tool. By using this formula in conjunction with the .loc function, you can easily assign values to a column based on complex criteria.

We hope this article has been informative and provided you with a clear understanding of how to use this formula in your own work. In summary, using the “if value in column then” formula in Pandas is a powerful tool for assigning values to a new column based on values in an existing column.

By using logical criteria to create the new column using the .loc function, you can easily handle complex computations and transformations in your data analysis. This article has provided a comprehensive breakdown of how to use this formula and has offered an example for illustration.

Additionally, resources such as the Pandas documentation, Pandas Cookbook, Data Wrangling with Pandas, and Pandas User Guide can aid in learning more about Pandas and refining your data manipulation skills. In conclusion, understanding how to use the “if value in column then” formula can significantly enhance your ability to work with data, and is a crucial concept to master for data manipulation tasks.