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

Ensembling by averaging


Within the context of regression models, the predictions are the numeric values of the variables of interest. Combining the predictions of the output due to the various ensemblers is rather straightforward; because of the ensembling mechanism, we simply interpret the average of the predicted values across the ensemblers as the predicted value. Within the context of the classification problem, we can carry out simple averaging and weighted averaging. In the previous section, the ensemble had homogeneous base learners. However, in this section, we will deal with heterogeneous base learners.

We will now consider a regression problem that is dealt with in detail in Chapter 8, Ensemble Diagnostics. The problem is the prediction of housing prices based on over 60 explanatory variables. We have the dataset in training and testing partitions, and load them to kick off the proceedings:

> # Averaging for Regression Problems
> load("../Data/ht_imp_author.Rdata") # returns...