Introduction

If you are familiar with the basics of machine learning, you will certainly know what supervised learning is all about. To give you a quick refresher, supervised learning refers to building a machine learning model that is based on labeled samples. For example, if we build a system to estimate the price of a house based on various parameters, such as size, locality, and so on, we first need to create a database and label it. We need to tell our algorithm what parameters correspond to what prices. Based on this data, our algorithm will learn how to calculate the price of a house using the input parameters.

Unsupervised learning is the opposite of what we just discussed. There is no labeled data available here. Let's assume that we have a bunch of datapoints, and we just want to separate them into multiple groups. We don't exactly know what the criteria of separation would be. So, an unsupervised learning algorithm will try to separate the given dataset into a fixed number of groups in the best possible way. We will discuss unsupervised learning in the upcoming chapters.

We will use various Python packages, such as NumPy, SciPy, scikit-learn, and matplotlib, during the course of this book to build various things. If you use Windows, it is recommended that you use a SciPy-stack compatible version of Python. You can check the list of compatible versions at http://www.scipy.org/install.html. These distributions come with all the necessary packages already installed. If you use Mac OS X or Ubuntu, installing these packages is fairly straightforward. Here are some useful links for installation and documentation:

• NumPy: http://docs.scipy.org/doc/numpy-1.10.1/user/install.html
• SciPy: http://www.scipy.org/install.html
• scikit-learn: http://scikit-learn.org/stable/install.html
• matplotlib: http://matplotlib.org/1.4.2/users/installing.html

Make sure that you have these packages installed on your machine before you proceed.