# Mastering Class-Based Box and Whisker Plots with the Caret Package in R

## Introduction

Data visualization is a crucial part of any data analysis or data science project. While density plots and scatter plots are often the go-to for data visualization, box and whisker plots offer a different kind of insight into your data. These plots are especially useful for understanding the distribution and spread of data points across different classes. In this article, we’ll delve into how to create class-based box and whisker plots using R’s Caret package, featuring the ever-popular Iris dataset as our example.

## The Caret Package in R

Caret stands for Classification And REgression Training, and it is one of the most widely used packages in R for machine learning and data visualization. It provides a consistent interface for a wide range of machine learning algorithms and is also equipped with functions for data visualization, including the ability to create box and whisker plots.

## A Brief Overview of the Iris Dataset

The Iris dataset contains 150 observations of iris flowers, each belonging to one of three species: setosa, versicolor, and virginica. Each observation comes with four attributes: sepal length, sepal width, petal length, and petal width.

## What Are Box and Whisker Plots?

Box and whisker plots (or box plots) provide a way to visualize the central tendency and spread of numerical data. They are particularly useful for identifying outliers, understanding distribution, and comparing multiple data sets. A box and whisker plot displays a summary of a set of data values based on quartiles, which divide a data set into four equal parts.

## Why Use Class-Based Box and Whisker Plots?

**1. Data Distribution:** Quickly gauge the spread and skewness of your data across different classes.

**2. Outlier Detection:** Easily spot outliers within each class for every feature.

**3. Comparative Analysis:** Assess how each attribute varies across different classes, which can be crucial for feature selection.

## Creating Class-Based Box and Whisker Plots in R

Here is the R code snippet that generates class-based box and whisker plots for the Iris dataset:

```
# Load the library
library(caret)
# Load the data
data(iris)
# Create box and whisker plots for each attribute by class value
featurePlot(x=iris[,1:4], y=iris[,5], plot="box", scales=list(x=list(relation="free"), y=list(relation="free")), auto.key=list(columns=3))
```

Code Explanation

**– Loading the Library:** `library(caret)` loads the Caret package into your R environment.

**– Loading the Data:** `data(iris)` loads the Iris dataset.

**– Creating Box and Whisker Plots:** The `featurePlot()` function from the Caret package is used to create the plots. The `plot=”box”` argument specifies that we want box and whisker plots. The `scales` argument allows different x and y scales for each subplot.

## End-to-End Example

Here’s a complete, step-by-step example:

```
# Install the Caret package if not already installed
# install.packages("caret")
# Load the Caret package
library(caret)
# Load the Iris dataset
data(iris)
# Create class-based box and whisker plots
featurePlot(x=iris[,1:4], y=iris[,5], plot="box", scales=list(x=list(relation="free"), y=list(relation="free")), auto.key=list(columns=3))
# Add a title
title(main="Class-Based Box and Whisker Plots of Iris Dataset Features", line=-1.5)
```

Conclusion

Class-based box and whisker plots offer an effective way to visualize and understand the distribution of attributes across different classes. With the Caret package in R, creating these plots becomes a straightforward task. Whether you’re a data science novice or a seasoned pro, using class-based box and whisker plots will deepen your understanding of your data and could lead to more accurate and insightful models.

## Find more … ..

Visualizing Class-Based Density Plots for Multi-Attribute Data in R with Caret

Year Seven Math Worksheet for Kids – Box Plots (Box and Whisker Plots)