Book Image

Practical Data Wrangling

By : Allan Visochek
Book Image

Practical Data Wrangling

By: Allan Visochek

Overview of this book

Around 80% of time in data analysis is spent on cleaning and preparing data for analysis. This is, however, an important task, and is a prerequisite to the rest of the data analysis workflow, including visualization, analysis and reporting. Python and R are considered a popular choice of tool for data analysis, and have packages that can be best used to manipulate different kinds of data, as per your requirements. This book will show you the different data wrangling techniques, and how you can leverage the power of Python and R packages to implement them. You’ll start by understanding the data wrangling process and get a solid foundation to work with different types of data. You’ll work with different data structures and acquire and parse data from various locations. You’ll also see how to reshape the layout of data and manipulate, summarize, and join data sets. Finally, we conclude with a quick primer on accessing and processing data from databases, conducting data exploration, and storing and retrieving data quickly using databases. The book includes practical examples on each of these points using simple and real-world data sets to give you an easier understanding. By the end of the book, you’ll have a thorough understanding of all the data wrangling concepts and how to implement them in the best possible way.
Table of Contents (16 chapters)
Title Page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Conducting basic outlier detection and removal


Outlier detection is a field of study in its own right, and deals with the detection of data that does not fit in a particular dataset. Advanced outlier detection techniques can be considered a part of data wrangling, but often draw from other fields, such as statistics and machine learning. For the purposes of this book, I will conduct a very basic form of outlier detection to find values that are too high. Values that are too high might be aggregates of the data or might reflect erroneous entries. 

In these next few steps, you will use the built-in plotting functionality in R to observe the data and look for particularly high values. 

The first step is to put the data in a form that can be easily visualized. A simple technique to capture the trend in the data by row is to find the means of all of the non-NA values in each data entry. This can be done using the rowMeans() function in R.

Before using the roawMeans() function, you will need to remove...