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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

Generative and discriminative models


In classification tasks, our goal is to learn the parameters of a model that optimally maps features of the explanatory variables to the response variable. All of the classifiers that we have previously discussed are discriminativemodels, which learn a decision boundary that is used to discriminate between classes. Probabilistic discriminative models, such as logistic regression, learn to estimate the conditional probability P(y|x); they learn to estimate which class is most likely given the input features. Non-probabilistic discriminative models, such as KNN, directly map features to classes.

Generative models do not directly learn a decision boundary. Instead, they model the joint probability distribution of the features and the classes, P(x, y). This is equivalent to modelling the probabilities of the classes and the probabilities of the features given the classes. That is, generative models model how the classes generate features. Bayes' theorem can...

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