Book Image

Data Science Projects with Python - Second Edition

By : Stephen Klosterman
Book Image

Data Science Projects with Python - Second Edition

By: Stephen Klosterman

Overview of this book

If data is the new oil, then machine learning is the drill. As companies gain access to ever-increasing quantities of raw data, the ability to deliver state-of-the-art predictive models that support business decision-making becomes more and more valuable. In this book, you’ll work on an end-to-end project based around a realistic data set and split up into bite-sized practical exercises. This creates a case-study approach that simulates the working conditions you’ll experience in real-world data science projects. You’ll learn how to use key Python packages, including pandas, Matplotlib, and scikit-learn, and master the process of data exploration and data processing, before moving on to fitting, evaluating, and tuning algorithms such as regularized logistic regression and random forest. Now in its second edition, this book will take you through the end-to-end process of exploring data and delivering machine learning models. Updated for 2021, this edition includes brand new content on XGBoost, SHAP values, algorithmic fairness, and the ethical concerns of deploying a model in the real world. By the end of this data science book, you’ll have the skills, understanding, and confidence to build your own machine learning models and gain insights from real data.
Table of Contents (9 chapters)
Preface

Model Performance on the Test Set

We already have some idea of the out-of-sample performance of the XGBoost model, from the validation set. However, the validation set was used in model fitting, via early stopping. The most rigorous estimate of expected future performance we can make should be created with data that was not used at all for model fitting. This was the reason for reserving a test dataset from the model building process.

You may notice that we did examine the test set to some extent already, for example, in the first chapter when assessing data quality and doing data cleaning. The gold standard for predictive modeling is to set aside a test set at the very beginning of a project and not examine it at all until the model is finished. This is the easiest way to make sure that none of the knowledge from the test set has "leaked" into the training set during model development. When this happens, it opens up the possibility that the test set is no longer a realistic...