Book Image

Data Science Using Python and R

By : Chantal D. Larose, Daniel T. Larose
Book Image

Data Science Using Python and R

By: Chantal D. Larose, Daniel T. Larose

Overview of this book

Data science is hot. Bloomberg named a data scientist as the ‘hottest job in America’. Python and R are the top two open-source data science tools using which you can produce hands-on solutions to real-world business problems, using state-of-the-art techniques. Each chapter in the book presents step-by-step instructions and walkthroughs for solving data science problems using Python and R. You’ll learn how to prepare data, perform exploratory data analysis, and prepare to model the data. As you progress, you’ll explore what are decision trees and how to use them. You’ll also learn about model evaluation, misclassification costs, naïve Bayes classification, and neural networks. The later chapters provide comprehensive information about clustering, regression modeling, dimension reduction, and association rules mining. The book also throws light on exciting new topics, such as random forests and general linear models. The book emphasizes data-driven error costs to enhance profitability, which avoids the common pitfalls that may cost a company millions of dollars. By the end of this book, you’ll have enough knowledge and confidence to start providing solutions to data science problems using R and Python.
Table of Contents (20 chapters)
Free Chapter
1
ABOUT THE AUTHORS
17
INDEX
18
END USER LICENSE AGREEMENT

12.6 HOW MANY COMPONENTS SHOULD WE EXTRACT?

Recall that one of the motivations for PCA was to reduce the dimensionality. The question arises, “How do we determine how many components to extract?” For example, should we retain only the first two principal components, since they explain over half (52% Cumulative Var) of the total variability? Or should we retain all five components, since they explain 100% of the variability? Well, clearly, retaining all five components does not help us to reduce the dimensionality. As usual, the answer lies somewhere between these two extremes.

12.6.1 The Eigenvalue Criterion

In Figure 12.8, the eigenvalues are labeled as “SS loadings.” An eigenvalue of 1.0 would mean that the component would explain about “one predictor’s worth” of the total variability. The rationale for using the eigenvalue criterion is that each component should explain at least one predictor's worth of the variability, and therefore...