Book Image

Applied Supervised Learning with R

By : Karthik Ramasubramanian, Jojo Moolayil
Book Image

Applied Supervised Learning with R

By: Karthik Ramasubramanian, Jojo Moolayil

Overview of this book

R provides excellent visualization features that are essential for exploring data before using it in automated learning. Applied Supervised Learning with R helps you cover the complete process of employing R to develop applications using supervised machine learning algorithms for your business needs. The book starts by helping you develop your analytical thinking to create a problem statement using business inputs and domain research. You will then learn different evaluation metrics that compare various algorithms, and later progress to using these metrics to select the best algorithm for your problem. After finalizing the algorithm you want to use, you will study the hyperparameter optimization technique to fine-tune your set of optimal parameters. The book demonstrates how you can add different regularization terms to avoid overfitting your model. By the end of this book, you will have gained the advanced skills you need for modeling a supervised machine learning algorithm that precisely fulfills your business needs.
Table of Contents (12 chapters)
Applied Supervised Learning with R
Preface

Constructing a Learner


A learner is a machine learning algorithm implementation in the mlr package. As highlighted in the previous section on the mlr package, there is a rich collection of such learner functions in mlr.

For our scene classification problem, the mlr package offers building a multilabel classification model in two possible ways:

  • Adaptation method: In this, we adapt an explicit algorithm on the entire problem.

  • Transformation method: We transform the problem into a simple binary classification problem and then apply the available algorithm for the binary classification.

Adaptation Methods

The mlr package in R offers two algorithm adaption methods. First, the multivariate random forest algorithm that comes from the randomForestSRC package, and second, the random ferns multilabel algorithm built in the rFerns package.

The makeLearner() function in mlr creates the model object for the rFerns and randomForestSRC algorithms, as shown in the following code:

multilabel.lrn3 = makeLearner...