{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Lecture23HO - CS440/ECE448 Intro to Articial Intelligence...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 23: Decision Trees Prof. Julia Hockenmaier [email protected] http://cs.illinois.edu/fa11/cs440 CS440/ECE448: Intro to ArtiFcial Intelligence Decision trees Decision trees 3 CS440/ECE448: Intro AI drink? milk? milk? coffee tea yes no no sugar sugar yes no sugar no sugar Decision tree learning Training data D = {( x 1 , y 1 ),…, ( x N , y N )} each x i = ( x 1 i ,…., x d i ) is a d -dimensional feature vector each y i is the target label (class) of the i-th data point Training algorithm: Initial tree = the root, corresponding to all items in D A node is a leaf if all its data items have the same y At each non-leaf node: Fnd the feature x i with the highest information gain, create a new child for each value of x i , distribute the items accordingly. 4 CS440/ECE448: Intro AI
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Information Gain How much information are we gaining by splitting node S on attribute A with values V(A) ? Information required before the split: H(S parent ) Information required after the split: ! i ˥ V(A) P(S child_i )H(S child_i ) Gain ( S parent , A ) = H ( S parent ) ! H ( S child i ) i " V ( A ) N # S child i S parent Dealing with numerical attributes Many attributes are not boolean (0,1) or nominal (classes) Number of times a word appears in a text RGB values of a pixel height, weight, ….
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 7

Lecture23HO - CS440/ECE448 Intro to Articial Intelligence...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon bookmark
Ask a homework question - tutors are online