Book Image

Hands-On Ensemble Learning with R

By : Prabhanjan Narayanachar Tattar
Book Image

Hands-On Ensemble Learning with R

By: Prabhanjan Narayanachar Tattar

Overview of this book

Ensemble techniques are used for combining two or more similar or dissimilar machine learning algorithms to create a stronger model. Such a model delivers superior prediction power and can give your datasets a boost in accuracy. Hands-On Ensemble Learning with R begins with the important statistical resampling methods. You will then walk through the central trilogy of ensemble techniques – bagging, random forest, and boosting – then you'll learn how they can be used to provide greater accuracy on large datasets using popular R packages. You will learn how to combine model predictions using different machine learning algorithms to build ensemble models. In addition to this, you will explore how to improve the performance of your ensemble models. By the end of this book, you will have learned how machine learning algorithms can be combined to reduce common problems and build simple efficient ensemble models with the help of real-world examples.
Table of Contents (17 chapters)
Hands-On Ensemble Learning with R
Contributors
Preface
12
What's Next?
Index

Interrating agreement


A simple extension of the measures discussed in the previous section on the ensemble classifiers is to compute the measures for all possible pairs of the ensemble and then simply average over all those values. This task constitutes the next exercise.

Exercise: For all possible combinations of ensemble pairs, calculate the disagreement measure, Yule's statistic, correlation coefficient, Cohen's kappa, and the double-fault measure. After doing this, obtain the average of the comparisons and report them as the ensemble diversity.

Here, we will propose alternative measures of diversity and kick-start the discussion with the entropy measure. In all discussions in this section, we will use the oracle outputs.

Entropy measure

You may recall that we denote the oracle outputs according to . For a particular instance, the ensemble is most diverse if the number of classifiers misclassifying it is . This means that of the s are 0s, and the rest of the , s are 1s. The entropy measure...