Book Image

Large Scale Machine Learning with Python

By : Bastiaan Sjardin, Alberto Boschetti
Book Image

Large Scale Machine Learning with Python

By: Bastiaan Sjardin, Alberto Boschetti

Overview of this book

Large Python machine learning projects involve new problems associated with specialized machine learning architectures and designs that many data scientists have yet to tackle. But finding algorithms and designing and building platforms that deal with large sets of data is a growing need. Data scientists have to manage and maintain increasingly complex data projects, and with the rise of big data comes an increasing demand for computational and algorithmic efficiency. Large Scale Machine Learning with Python uncovers a new wave of machine learning algorithms that meet scalability demands together with a high predictive accuracy. Dive into scalable machine learning and the three forms of scalability. Speed up algorithms that can be used on a desktop computer with tips on parallelization and memory allocation. Get to grips with new algorithms that are specifically designed for large projects and can handle bigger files, and learn about machine learning in big data environments. We will also cover the most effective machine learning techniques on a map reduce framework in Hadoop and Spark in Python.
Table of Contents (17 chapters)
Large Scale Machine Learning with Python
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Index

Feature decomposition – PCA


PCA is an algorithm commonly used to decompose the dimensions of an input signal and keep just the principal ones. From a mathematical perspective, PCA performs an orthogonal transformation of the observation matrix, outputting a set of linear uncorrelated variables, named principal components. The output variables form a basis set, where each component is orthonormal to the others. Also, it's possible to rank the output components (in order to use just the principal ones) as the first component is the one containing the largest possible variance of the input dataset, the second is orthogonal to the first (by definition) and contains the largest possible variance of the residual signal, and the third is orthogonal to the first two and it's built on the residual variance, and so on.

A generic transformation with PCA can be expressed as a projection to a space. If just the principal components are taken from the transformation basis, the output space will have a...