Pandas DataFrame Idxmin Method

Introduction

In this lab, we will explore and understand the DataFrame.idxmin() method in Python pandas. This method is used to retrieve the index of the first occurrence of the minimum value along a specified axis. It excludes any null or missing values. The method returns a series that contains the indexes of the minima along the specified axis.

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Skills Graph

Create a DataFrame

First, we need to create a DataFrame to work with. In this step, we import the pandas library and create a DataFrame with two columns: 'Marks_1' and 'Marks_2'. The DataFrame has three rows, each representing a subject (Kannada, English, Science) and the respective marks.

import pandas as pd

## Create DataFrame
df = pd.DataFrame({'Marks_1': [85, 90, 45], 'Marks_2': [85, 96, 100]}, index=['Kannada', 'English', 'Science'])

## Print DataFrame
print("---- The DataFrame is ----")
print(df)

Find Index of Minimum Value Over the Row Axis

In this step, we use the DataFrame.idxmin() method to find the index of the minimum value over the row axis. We apply the method on the DataFrame and print the result.

## Find index of minimum value over row axis
print("---- Index of the minimum value over the row axis ----")
print(df.idxmin())

Find Index of Minimum Value Over the Column Axis

In this step, we use the DataFrame.idxmin() method to find the index of the minimum value over the column axis. We apply the method on the DataFrame specifying axis="columns" and print the result.

## Find index of minimum value over column axis
print("---- Index of the minimum value over the column axis ----")
print(df.idxmin(axis="columns"))

Handle Null Values

In this step, we create a DataFrame with null values and apply the DataFrame.idxmin() method. We want to see how the method handles null values. We print the resulting series.

## Create DataFrame with null values
df = pd.DataFrame({'Marks_1': [85, None, 45], 'Marks_2': [None, 46, None]}, index=['Kannada', 'English', 'Science'])

## Print DataFrame
print("---- The DataFrame is ----")
print(df)

## Find index of minimum value over column axis
print("---- Index of the minimum value over the column axis ----")
print(df.idxmin(axis="columns"))

Summary

In this lab, we explored the Python pandas DataFrame.idxmin() method. We learned how to find the index of the first occurrence of the minimum value along a specified axis. We also saw how the method handles null values. The DataFrame.idxmin() method is a useful tool to retrieve the indexes of minima in a DataFrame.