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Hands-On Machine Learning with scikit-learn and Scientific Python Toolkits

You're reading from   Hands-On Machine Learning with scikit-learn and Scientific Python Toolkits A practical guide to implementing supervised and unsupervised machine learning algorithms in Python

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Product type Paperback
Published in Jul 2020
Publisher Packt
ISBN-13 9781838826048
Length 384 pages
Edition 1st Edition
Languages
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Author (1):
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Tarek Amr Tarek Amr
Author Profile Icon Tarek Amr
Tarek Amr
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Table of Contents (18) Chapters Close

Preface 1. Section 1: Supervised Learning
2. Introduction to Machine Learning FREE CHAPTER 3. Making Decisions with Trees 4. Making Decisions with Linear Equations 5. Preparing Your Data 6. Image Processing with Nearest Neighbors 7. Classifying Text Using Naive Bayes 8. Section 2: Advanced Supervised Learning
9. Neural Networks – Here Comes Deep Learning 10. Ensembles – When One Model Is Not Enough 11. The Y is as Important as the X 12. Imbalanced Learning – Not Even 1% Win the Lottery 13. Section 3: Unsupervised Learning and More
14. Clustering – Making Sense of Unlabeled Data 15. Anomaly Detection – Finding Outliers in Data 16. Recommender System – Getting to Know Their Taste 17. Other Books You May Enjoy

Outlier and novelty detection using LOF

"Madness is rare in individuals – but in groups, parties, nations, and ages, it is the rule."
– Friedrich Nietzsche

LOF takes an opposite approach to Nietzsche's—it compares the density of a sample to the local densities of its neighbors. A sample existing in a low-density area compared to its neighbors is considered an outlier. Like any other neighbor-based algorithms, we have parameters to specify the number of neighbors to consider (n_neighbors) and the distance metric to use to find the neighbors (metric and p). By default, the Euclidean distance is used—that is, metric='minkowski' and p=2. You can refer to Chapter 5, Image Processing with Nearest Neighbors, for more information about the available distance metrics. Here is how we useLocalOutlierFactor for outlier detection, using 50 neighbors and its default distance metric:

from sklearn.neighbors import LocalOutlierFactor...
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