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Mastering Machine Learning with scikit-learn. - Second Edition

You're reading from  Mastering Machine Learning with scikit-learn. - Second Edition

Product type Book
Published in Jul 2017
Publisher
ISBN-13 9781788299879
Pages 254 pages
Edition 2nd Edition
Languages
Author (1):
Gavin Hackeling Gavin Hackeling
Profile icon Gavin Hackeling
Toc

Table of Contents (22) Chapters close

Title Page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
1. The Fundamentals of Machine Learning 2. Simple Linear Regression 3. Classification and Regression with k-Nearest Neighbors 4. Feature Extraction 5. From Simple Linear Regression to Multiple Linear Regression 6. From Linear Regression to Logistic Regression 7. Naive Bayes 8. Nonlinear Classification and Regression with Decision Trees 9. From Decision Trees to Random Forests and Other Ensemble Methods 10. The Perceptron 11. From the Perceptron to Support Vector Machines 12. From the Perceptron to Artificial Neural Networks 13. K-means 14. Dimensionality Reduction with Principal Component Analysis Index

Maximum margin classification and support vectors


The following figure depicts instances from two linearly separable classes and three possible decision boundaries. All of the decision boundaries separate the training instances of the positive class from the training instances of the negative class, and a perceptron can learn any of them. Which of these decision boundaries is most likely to perform best on test data?

From this visualization, it is intuitive that the dotted decision boundary is the best. The solid decision boundary is near many of the positive instances. The test set could contain a positive instance that has a slightly smaller value for the first explanatory variable, x1; this instance would be classified incorrectly. The dashed decision boundary is farther away from most of the training instances; however, it is near one of the positive instances and one of the negative instances.

The previous figure provides a different perspective on evaluating decision boundaries. Assume...

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