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Mastering Machine Learning with scikit-learn

Mastering Machine Learning with scikit-learn

By : Gavin Hackeling
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Mastering Machine Learning with scikit-learn

Mastering Machine Learning with scikit-learn

5 (2)
By: Gavin Hackeling

Overview of this book

Machine learning is the buzzword bringing computer science and statistics together to build smart and efficient models. Using powerful algorithms and techniques offered by machine learning you can automate any analytical model. This book examines a variety of machine learning models including popular machine learning algorithms such as k-nearest neighbors, logistic regression, naive Bayes, k-means, decision trees, and artificial neural networks. It discusses data preprocessing, hyperparameter optimization, and ensemble methods. You will build systems that classify documents, recognize images, detect ads, and more. You will learn to use scikit-learn’s API to extract features from categorical variables, text and images; evaluate model performance, and develop an intuition for how to improve your model’s performance. By the end of this book, you will master all required concepts of scikit-learn to build efficient models at work to carry out advanced tasks with the practical approach.
Table of Contents (15 chapters)
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9
From Decision Trees to Random Forests and Other Ensemble Methods

Regularization


Regularization is a collection of techniques that can be used to prevent overfitting. Regularization adds information, often in the form of a penalty against complexity, to a problem. Occam's razor states that the hypothesis with the fewest assumptions is best. Accordingly, regularization attempts to find the simplest model that explains the data.

scikit-learn provides several regularized linear regression models. Ridge regression, also known as Tikhonov regularization, penalizes model parameters that become too large. Ridge regression modifies the RSS cost function by adding the L2 norm of the coefficients, as follows:

Lambda is a hyperparameter that controls the strength of the penalty. Recall from Chapter 3, Classification and Regression with K-Nearest Neighbors, that hyperparameters are parameters of the model that control how the learning algorithm learns. As lambda increases, the penalty increases, and the value of the cost function increases. When lambda is equal to zero...

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