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

Chapter 2. Bootstrapping

As seen in the previous chapter, statistical inference is enhanced to a very large extent with the use of computational power. We also looked at the process of permutation tests, wherein the same test is applied multiple times for the resamples of the given data under the (null) hypothesis. The rationale behind resampling methods is also similar; we believe that if the sample is truly random and the observations are generated from the same identical distribution, we have a valid reason to resample the same set of observations with replacements. This is because any observation might as well occur multiple times rather than as a single instance.

This chapter will begin with a formal definition of resampling, followed by a look at the jackknife technique. This will be applied to multiple, albeit relatively easier, problems, and we will look at the definition of the pseudovalues first. The bootstrap method, invented by Efron, is probably the most useful resampling method...