DECISION TREE Ge Song. Introduction ■ Decision Tree: is a supervised learning algorithm used for...
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Transcript of DECISION TREE Ge Song. Introduction ■ Decision Tree: is a supervised learning algorithm used for...
DECISION TREEGe Song
Introduction■ Decision Tree: is a supervised learning algorithm used for classification or
regression.
■ Decision Tree Graph: is a graph that uses a branching method to illustrate every possible outcome of a decision.
input
output
Each internal node: test one discrete-valued attribute Xi Each branch from a node: selects one value for XiEach leaf node: predict Y (or P(Y|X leaf)) ∈
ID3 Algorithm
■Calculate the entropy of every attribute using the data set
■Split the set into subsets using the attribute for which entropy is minimum (or, equivalently, information gain is maximum)
■Make a decision tree node containing that attribute
■Recurse on subsets using remaining attributes.
Result and Limitations■ Result: [18+/13-]
H01420 = yes: [2+/12-]
| D12765 = yes: [2+/0-]
| D12765 = no: [0+/12-]
H01420 = no: [16+/1-]
| D14662 = yes: [0+/1-]
| D14662 = no: [16+/0-]
testError: 0.4
■ Limitation:
1) The rule (average max and min) that converts attribute values to binary values;
2) The threshold (0.1) that used to check whether to split or not ;
3) The depth of the tree and the robustness;
4) The cross validation step.