Book Image

Python Machine Learning By Example - Second Edition

By : Yuxi (Hayden) Liu
Book Image

Python Machine Learning By Example - Second Edition

By: Yuxi (Hayden) Liu

Overview of this book

The surge in interest in machine learning (ML) is due to the fact that it revolutionizes automation by learning patterns in data and using them to make predictions and decisions. If you’re interested in ML, this book will serve as your entry point to ML. Python Machine Learning By Example begins with an introduction to important ML concepts and implementations using Python libraries. Each chapter of the book walks you through an industry adopted application. You’ll implement ML techniques in areas such as exploratory data analysis, feature engineering, and natural language processing (NLP) in a clear and easy-to-follow way. With the help of this extended and updated edition, you’ll understand how to tackle data-driven problems and implement your solutions with the powerful yet simple Python language and popular Python packages and tools such as TensorFlow, scikit-learn, gensim, and Keras. To aid your understanding of popular ML algorithms, the book covers interesting and easy-to-follow examples such as news topic modeling and classification, spam email detection, stock price forecasting, and more. By the end of the book, you’ll have put together a broad picture of the ML ecosystem and will be well-versed with the best practices of applying ML techniques to make the most out of new opportunities.
Table of Contents (15 chapters)
Free Chapter
1
Section 1: Fundamentals of Machine Learning
3
Section 2: Practical Python Machine Learning By Example
12
Section 3: Python Machine Learning Best Practices

Topic modeling using NMF

Non-negative matrix factorization (NMF) relies heavily on linear algebra. It factorizes an input matrix, V, into a product of two smaller matrices, W and H, in such a way that these three matrices have no negative values. In the context of NLP, these three matrices have the following meanings:

  • The input matrix V is the term counts or tf-idf matrix of size n * m, where n is the number of documents or samples, and m is the number of terms.
  • The first decomposition output matrix W is the feature matrix of size t * m, where t is the number of topics specified. Each row of W represents a topic with each element in the row representing the rank of a term in the topic.
  • The second decomposition output matrix H is the coefficient matrix of size n * t. Each row of H represents a document, with each element in the row representing the weight of a topic within the...