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

Exploring the contents of a data file


Before writing code to process a dataset, you first need to know some information about the contents of the dataset. This is slightly different from exploratory data analysis, in which the goal is to draw insight from the data.

The details of your initial exploration generally depend on what you already know about a particular dataset and what you ultimately intend to do with the data. That being said, there are a few questions that are usually helpful to ask:

  • How is the data structured?
    • If the dataset is tabular, the answer to this question is rather simple. However, for a hierarchical dataset, there may be a relatively loose structure of the data.
  • What are the data variables?
  • For each available variable, what is the data type and what is the range of possible values?
  • Are there any errors, missing values, or outliers in the data that can be corrected?

It is not always necessary to do this exploration programmatically. However, often files are too big or messy...