# Reduced Error Pruning Wiki

classify instances. Pruning reduces the complexity of the final classifier, and hence improves predictive accuracy by the reduction of overfitting. This article includes a list of references, but its sources remain unclear because it has insufficient decision tree pruning example inline citations. Please help to improve this article by introducing more precise citations. (May 2008)

## Pre Pruning And Post Pruning In Decision Tree

(Learn how and when to remove this template message) Contents 1 Introduction 2 Techniques 2.1 Reduced error pruning 2.2 Cost complexity

## Decision Tree Pruning Tutorial

pruning 3 See also 4 References 5 Further reading 6 External links Introduction[edit] One of the questions that arises in a decision tree algorithm is the optimal size of the final tree. A tree that is

## Cost Complexity Pruning Example

too large risks overfitting the training data and poorly generalizing to new samples. A small tree might not capture important structural information about the sample space. However, it is hard to tell when a tree algorithm should stop because it is impossible to tell if the addition of a single extra node will dramatically decrease error. This problem is known as the horizon effect. A common strategy is to grow the tree until pessimistic pruning each node contains a small number of instances then use pruning to remove nodes that do not provide additional information.[1] Pruning should reduce the size of a learning tree without reducing predictive accuracy as measured by a cross-validation set. There are many techniques for tree pruning that differ in the measurement that is used to optimize performance. Techniques[edit] Pruning can occur in a top down or bottom up fashion. A top down pruning will traverse nodes and trim subtrees starting at the root, while a bottom up pruning will start at the leaf nodes. Below are several popular pruning algorithms. Reduced error pruning[edit] One of the simplest forms of pruning is reduced error pruning. Starting at the leaves, each node is replaced with its most popular class. If the prediction accuracy is not affected then the change is kept. While somewhat naive, reduced error pruning has the advantage of simplicity and speed. Cost complexity pruning[edit] Cost complexity pruning generates a series of trees T0 . . . Tm where T0 is the initial tree and Tm is the root alone. At step i the tree is created by removing a subtree from tree i-1 and replacing it with a leaf node with value chosen as in the tree building algorithm. The subtree that is rem

example of a decision tree pruning to overcome overfitting?I have found this link but it is not very descriptive. I am looking for something which shows how each step of pruning is done. http://www.cs.waikato.ac.nz/~eib...UpdateCancelAnswer Wiki1 Answer Abhishek reduced error pruning algorithm Ghose, Data Scientist @[24]7Updated 108w agoThere is more than one way to perform pruning. pruning decision tree in r The particular figure you have provided is an example of Quinlan's Reduced Error Pruning. Roughly this is how it works:Keep aside a tree pruning in data mining examples part of the dataset for post-pruning of the tree. This is different from the test set and is known as the pruning set.For a subtree S of the tree, if replacing S by a leaf does https://en.wikipedia.org/wiki/Pruning_(decision_trees) not make more prediction errors on the pruning set than the original tree, replace S by a leaf.Perform step 2 only when no subtree of S possesses the property mentioned in 2.Because of 3, you need to proceed in a bottom up manner - so that if there is a subtree of S, say S', that can be replaced by a leaf, then it must be replaced by a leaf first - so https://www.quora.com/How-can-I-find-a-real-step-by-step-example-of-a-decision-tree-pruning-to-overcome-overfitting that after replacement, S does not have any subtree with this property, and can go ahead and potentially replace S if needed.In the diagram, note that the pruning happens bottom-up and left-to-right. Every node notes the number of samples it misclassifies in parenthesis. For ex in fig 3.3 (a), the node in marked in red misclasssifies one example from the pruning set:Misclassified example in the pruning set:Starting from the bottom its easy to see that node 3 can be made into a leaf since it makes lesser errors (on the pruning set) than as a subtree - as a subtree the classification happens at nodes 4 and 5, and 5 makes one error; node 3 by itself makes no errors. Same goes for 6 and 9. However, 2 cannot be made into a leaf since it makes one error, while as a subtree, with the newly-created leaves 3 and 6 it makes no errors. Final tree:For more details you may want to refer to the paper "Simplifying Decision Trees" by Quinlan.1.2k Views · View UpvotesView More AnswersRelated QuestionsDecision Trees: How do you prune a CART?What is the simple explanation of entropy as used in decision trees?Is there a machine learning book which gives a step by step guide with real number or numerical examples in machine learni

1.1.2 1.2. Prune phase: 1.2 2. Optimization stage: 2 Installation 3 Example 4 Study Case 4.1 Dataset 4.2 Execution and Results 4.3 Output 4.4 Result 4.5 References Synopsis[edit] This class implements a propositional rule https://en.wikibooks.org/wiki/Data_Mining_Algorithms_In_R/Classification/JRip learner, Repeated Incremental Pruning to Produce Error Reduction (RIPPER), which was proposed by William W. Cohen as an optimized version of IREP. It is based in association rules with reduced error pruning (REP), a very common and effective technique found in decision tree algorithms. In REP for rules algorithms, the training data is split into a growing set and a pruning set. First, an initial rule set is decision tree formed that over ts the growing set, using some heuristic method. This overlarge rule set is then repeatedly simplified by applying one of a set of pruning operators typical pruning operators would be to delete any single condition or any single rule. At each stage of simplification, the pruning operator chosen is the one that yields the greatest reduction of error on the pruning set. Simplification ends when reduced error pruning applying any pruning operator would increase error on the pruning set. The algorithm is briefly described as follows: Initialize RS = {}, and for each class from the less prevalent one to the more frequent one, DO: 1. Building stage:[edit] Repeat 1.1 and 1.2 until the description length (DL) of the rule set and examples is 64 bits greater than the smallest DL met so far, or there are no positive examples, or the error rate >= 50%. 1.1. Grow phase:[edit] Grow one rule by greedily adding antecedents (or conditions) to the rule until the rule is perfect (i.e. 100% accurate). The procedure tries every possible value of each attribute and selects the condition with highest information gain: p(log(p/t)-log(P/T)). 1.2. Prune phase:[edit] Incrementally prune each rule and allow the pruning of any final sequences of the antecedents;The pruning metric is (p-n)/(p+n) – but it's actually 2p/(p+n) -1, so in this implementation we simply use p/(p+n) (actually (p+1)/(p+n+2), thus if p+n is 0, it's 0.5). 2. Optimization stage:[edit] after generating the initial rule set {Ri}, generate and prune two variants of each rule Ri from randomized data using procedure 1.1 and 1.2. But one variant is generated from an empty rule while the

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Reduced Error Pruning Algorithm p classify instances Pruning reduces the complexity of the final classifier and hence improves predictive accuracy by the reduction of reduced error pruning example overfitting This article includes a list of references but its sources decision tree pruning tutorial remain unclear because it has insufficient inline citations Please help to improve this article by introducing more pre pruning and post pruning in decision tree precise citations May Learn how and when to remove this template message Contents Introduction Techniques Reduced error pruning Cost complexity pruning See cost complexity pruning also References Further reading External links Introduction

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Reduced Error Pruning Decision Trees Examples p classify instances Pruning reduces the complexity of the final classifier and hence improves predictive accuracy by the reduction of overfitting This article includes a list decision tree pruning tutorial of references but its sources remain unclear because it has insufficient inline p Pre Pruning And Post Pruning In Decision Tree p citations Please help to improve this article by introducing more precise citations May Learn how and when reduced error pruning algorithm to remove this template message Contents Introduction Techniques Reduced error pruning Cost complexity pruning See also References Further reading External links

reduced error pruning in decision trees

Reduced Error Pruning In Decision Trees p Exercise Advanced Topics Evaluating Decision Trees Exercise Overfitting Pruning Exercise Further Topics pre pruning and post pruning in decision tree Conclusion Software Data Sets Books Papers Sites Feeds About Contact Decision Trees decision tree pruning tutorial Tutorial Pruning Pruning to avoid overfitting The approach to constructing decision trees usually involves using greedy heuristics such as reduced error pruning algorithm Entropy reduction that overfit the training data and lead to poor accuracy in future predictions In response to the problem of overfitting nearly all modern decision tree algorithms adopt a pruning strategy p Cost

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Reduced Error Pruning Advantages p classify instances Pruning reduces the complexity of the final classifier and hence improves predictive accuracy by the reduction of overfitting This article includes decision tree pruning example a list of references but its sources remain unclear because it has pre pruning and post pruning in decision tree insufficient inline citations Please help to improve this article by introducing more precise citations May Learn how p Pruned Meaning In English p and when to remove this template message Contents Introduction Techniques Reduced error pruning Cost complexity pruning See also References Further reading p Decision Tree Pruning

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Reduced Error Pruning Tutorial p classify instances Pruning reduces the complexity of the final classifier and hence improves predictive accuracy by the reduction of overfitting This article includes a list of references but its sources remain unclear because it has insufficient inline citations p Reduced Error Pruning Decision Trees Examples p Please help to improve this article by introducing more precise citations May Learn decision tree pruning tutorial how and when to remove this template message Contents Introduction Techniques Reduced error pruning Cost complexity pruning pessimistic pruning See also References Further reading External links Introduction edit One of the questions

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Reduced Error Pruning Examples p Help pages Full-text links Download PDF PostScript license Current browse context cs AI prev next new recent Change to browse by cs References CitationsNASA ADS DBLP - CS p Decision Tree Pruning Tutorial p Bibliography listing bibtex Tapio Elomaa Matti K xE xE ri xE inen Bookmark what is this pessimistic pruning Computer Science Artificial Intelligence Title An Analysis of Reduced Error Pruning Authors T Elomaa M Kaariainen Submitted reduced error pruning algorithm on Jun Abstract Top-down induction of decision trees has been observed to suffer from the inadequate functioning of the pruning phase In

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Reduced Error Pruning Decision Trees p Exercise Advanced Topics Evaluating Decision Trees Exercise Overfitting Pruning Exercise Further Topics pre pruning and post pruning in decision tree Conclusion Software Data Sets Books Papers Sites Feeds About Contact Decision Trees Tutorial decision tree pruning tutorial Pruning Pruning to avoid overfitting The approach to constructing decision trees usually involves using greedy heuristics such as cost complexity pruning example Entropy reduction that overfit the training data and lead to poor accuracy in future predictions In response to the problem of overfitting nearly all modern decision tree algorithms adopt a pruning strategy of p Reduced

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Reduced Error Pruning And Rule Post Pruning p result in improved estimated accuracy Sort the pruned rules by their estimated accuracy and consider them in this sequence when classifying unseen instances Patricia Riddle Fri May NZST p p here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn p Pruning Decision Tree In R p more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users decision

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Tree Misclassification Error p years sibsp number of siblings or spouses aboard parch number of parents or children aboard span p Classification Error Rate Decision Tree p class kw library span rpart span class kw library span rpart plot span class kw data span ptitanic span class kw str span ptitanic 'data frame' obs what is root node error of variables pclass Factor w levels st nd rd how to calculate accuracy of a decision tree survived Factor w levels died survived p Root Node Error Decision Tree p sex Factor w levels female male age Class 'labelled' atomic -