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

Missing data imputation


Missing data is a menace! It pops up out of nowhere and blocks analysis until it is properly taken care of. The statistical technique of the expectation-maximization algorithm, or simply the EM algorithm, needs a lot of information on the probability distributions, structural relationship, and in-depth details of statistical models. However, an approach using the EM algorithm is completely ruled out here. Random forests can be used to overcome the missing data problem.

We will use the missForest R package to fix the missing data problem whenever we come across it in the rest of the book. The algorithm for the missForest function and other details can be found at https://academic.oup.com/bioinformatics/article/28/1/112/219101. For any variable/column with missing data, the technique is to build a random forest for that variable and obtain the OOB prediction as the imputation error estimates. Note that the function can handle continuous as well as categorical missing...