Book Image

Julia for Data Science

By : Anshul Joshi
2 (1)
Book Image

Julia for Data Science

2 (1)
By: Anshul Joshi

Overview of this book

Julia is a fast and high performing language that's perfectly suited to data science with a mature package ecosystem and is now feature complete. It is a good tool for a data science practitioner. There was a famous post at Harvard Business Review that Data Scientist is the sexiest job of the 21st century. (https://hbr.org/2012/10/data-scientist-the-sexiest-job-of-the-21st-century). This book will help you get familiarised with Julia's rich ecosystem, which is continuously evolving, allowing you to stay on top of your game. This book contains the essentials of data science and gives a high-level overview of advanced statistics and techniques. You will dive in and will work on generating insights by performing inferential statistics, and will reveal hidden patterns and trends using data mining. This has the practical coverage of statistics and machine learning. You will develop knowledge to build statistical models and machine learning systems in Julia with attractive visualizations. You will then delve into the world of Deep learning in Julia and will understand the framework, Mocha.jl with which you can create artificial neural networks and implement deep learning. This book addresses the challenges of real-world data science problems, including data cleaning, data preparation, inferential statistics, statistical modeling, building high-performance machine learning systems and creating effective visualizations using Julia.
Table of Contents (17 chapters)
Julia for Data Science
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface

Scatter matrix and covariance


Covariance is used very often by data scientists to find out how two ordered sets of data follow in the same direction. It can very easily define whether the variables are correlated or not. To best represent this behavior, we create a covariance matrix. The unnormalized version of the covariance matrix is the scatter matrix.

To create a scatter matrix, we use the scattermat(arr) function.

The default behavior is to treat each row as an observation and column as a variable. This can be changed by providing the keyword arguments vardim and mean:

  • Vardim: vardim=1 (default) means each column is a variable and each row is an observation. vardim=2 is the reverse.

  • mean: The mean is computed by scattermat. We can use a predefined mean to save compute cycles.

We can also create a weighted covariance matrix using the cov function. It also takes vardim and mean as optional arguments for the same purpose.