Meat NY Crust D,S,T Veg Quality NY B,G,Gr Decision Tree Homework Y Thin N Great N Deep Bad 10 < Z N Stuffed Good Info(S) - pilogzpi Y Stuffed Y Great Y Deep N Good i=1 Y Deep Y Great N Thin Y Good Y Deep N Good N Thin N Bad i=1 |A| SI |s; InfoA(S) Info(S;) - 18 Pilogzpi SL Info(S) = - 2/9.log22/9 - 4/9.log24/9-3/9.log23/9 = 1.53 Not necessary unless you want to calculate information gain Starting with all instances, calculate gain for each attribute Let's do Meat: Info Meat (S) = 4/9.(-2/4log22/4 - 2/4.log22/4 - 0 log20/4)+ 5/9:(-0/5log20/5 - 2/5log22/5 - 3/5 log23/5) = .98 Information Gain is 1.53 - .98 = .55 Finish this level, find best attribute and split, and then find the best attribute for at least the left most node at the next level Assume sub-nodes are sorted alphabetically left to right by attribute