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Python Machine Learning By Example
book

Python Machine Learning By Example

by Yuxi (Hayden) Liu, Ivan Idris
May 2017
Beginner to intermediate content levelBeginner to intermediate
254 pages
6h 24m
English
Packt Publishing
Content preview from Python Machine Learning By Example

The implementations of decision tree

With a solid understanding of partitioning evaluation metrics, let's practice the CART tree algorithm by hand on a simulated dataset:

To begin, we decide on the first splitting point, the root, by trying out all possible values for each of two features. We utilize the weighted_impurity function we just defined to calculate the weighted Gini impurity for each possible combination:

Gini(interest, Tech) = weighted_impurity([[1, 1, 0], [0, 0, 0, 1]]) = 0.405

Gini(interest, Fashion) = weighted_impurity([[0, 0], [1, 0, 1, 0, 1]]) = 0.343

Gini(interest, Sports) = weighted_impurity([[0, 1], [1, 0, 0, 1, 0]]) = ...

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Publisher Resources

ISBN: 9781783553112Supplemental Content