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

13.5 POISSON REGRESSION

There are many other kinds of regression models that fall under the umbrella of GLM. We will examine one other: Poisson regression. Poisson regression is used when you want to predict a count of events, such as how many times a customer will contact customer service. The distribution of the response variable will be a count of occurrences, with a minimum value of zero.

The link function for a count response variable is g(μ) = ln(μ). We set the link function equal to our linear predictor to obtain

equationXβ=ln(μ)--

After isolating μ, we have

equationμ=eXβ--

Working backwards from our abbreviated notation, we find the parametric version of the Poisson regression equation

equationy=eβ0+β1x1+β2x2++βpxp+ε--

from which we can write the descriptive form

equationy^=eb0+b1x1+b2x2++bpxp--