Book Image

Learning Predictive Analytics with R

By : Eric Mayor
Book Image

Learning Predictive Analytics with R

By: Eric Mayor

Overview of this book

This book is packed with easy-to-follow guidelines that explain the workings of the many key data mining tools of R, which are used to discover knowledge from your data. You will learn how to perform key predictive analytics tasks using R, such as train and test predictive models for classification and regression tasks, score new data sets and so on. All chapters will guide you in acquiring the skills in a practical way. Most chapters also include a theoretical introduction that will sharpen your understanding of the subject matter and invite you to go further. The book familiarizes you with the most common data mining tools of R, such as k-means, hierarchical regression, linear regression, association rules, principal component analysis, multilevel modeling, k-NN, Naïve Bayes, decision trees, and text mining. It also provides a description of visualization techniques using the basic visualization tools of R as well as lattice for visualizing patterns in data organized in groups. This book is invaluable for anyone fascinated by the data mining opportunities offered by GNU R and its packages.
Table of Contents (23 chapters)
Learning Predictive Analytics with R
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Exercises and Solutions
Index

C4.5


C4.5 works in ways similar to ID3, but uses the gain ratio as a partitioning criterion, which in part resolves the issue mentioned previously. Another advantage is that it accepts partition on numeric attributes, which it splits into categories. The value of the split is selected in order to decrease the entropy for the considered attribute. Other differences from ID3 are that C4.5 allows for post-pruning, which is basically the bottom up simplification of the tree to avoid overfitting to the training data.

The gain ratio

Using the gain ratio as partitioning criterion overcoming a shortcomes of ID3, which is to prefer attributes with many modalities as nodes because they have a higher information gain. The gain ratio divides the information gain by a value called split information. This value is computed as minus the sum of: the ratio of the number of cases in each modality of the attribute divided by the number of cases to partition upon, multiplied by the base 2 logarithm of the number...