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Hands-On Ensemble Learning with R

Hands-On Ensemble Learning with R

By : Tattar
3 (1)
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Hands-On Ensemble Learning with R

Hands-On Ensemble Learning with R

3 (1)
By: 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 (15 chapters)
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12
12. What's Next?
13
A. Bibliography
14
Index

Chapter 4. Random Forests

The previous chapter introduced bagging as an ensembling technique based on homogeneous base learners, with the decision tree serving as a base learner. A slight shortcoming of the bagging method is that the bootstrap trees are correlated. Consequently, although the variance of predictions is reduced, the bias will persist. Breiman proposed randomly sampling the covariates and independent variables at each split, and this method then went on to help in decorrelating the bootstrap trees.

In the first section of this chapter, the random forest algorithm is introduced and illustrated. The notion of variable importance is crucial to decision trees and all of their variants, and a section is devoted to clearly illustrating this concept. Do the random forests perform better than bagging? An answer will be provided in the following section.

Breiman laid out the importance of proximity plots in the context of random forests, and we will delve into this soon enough...

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