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

7.1 INTRODUCTION TO MODEL EVALUATION

So far in Data Science Using Python and R, we have covered the first five phases of the Data Science Methodology:

  1. Data Understanding Phase
  2. Data Preparation Phase
  3. Exploratory Data Analysis Phase
  4. Setup Phase
  5. Modeling Phase (at least a little bit)

But, so far we have not examined whether our models are any good. That is, we have not evaluated their usefulness in making predictions. Note the difference between evaluation and validation. Model validation simply makes sure that our model results are consistent between the training and test data sets. But, model validation does not tell us how accurate our models are, or what their error rate is. For measures like these, we need to turn to model evaluation. Since the only models we have learned so far are decision trees for classification, we shall restrict our discussion to evaluative measures for classification models.