Lect20 - Announcement HW4 on BNs due Tuesday Machine...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
Announcement HW4 on BNs due Tuesday Machine Learning Next Chapters 18 & 20 in text
Background image of page 1

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

View Full DocumentRight Arrow Icon
Naïve Bayes Symptoms (attributes) are conditionally independent of each other given the Disease (classification) Stringent assumptions / Impoverished expressiveness Works surprisingly (?) well in practice Common first choice NOTE the use of intentionally impoverished model (for tractability - recall coffee cup)
Background image of page 2
Naïve Bayes Symptom1 (T/F) Disease (1,2,3,…) Symptom2 (T/F) Symptom3 (T/F) P(d 1 ) P(d 2 ) P(d 3 )    P(s 1 |d 1 ) P(s 1 |d 2 ) P(s 1 |d 3 )    P(s 2 |d 1 ) P(s 2 |d 2 ) P(s 2 |d 3 )    P(s 3 |d 1 ) P(s 3 |d 2 ) P(s 3 |d 3 )    Infer likely disease:   S d P i d i | max arg
Background image of page 3

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

View Full DocumentRight Arrow Icon
Naïve Bayes Diagnose by inference with: |D| Functions, each assigns probability over the Boolean hypercube Which are / are not probability models? Fourth is not normalized (why does that work?) Parameters are adjusted to best fit the world samples What are the parameters? A kind of machine learning We will consider the probability functions the log probability functions the decision boundaries j i j i d j i j i d i i d i d d s P d P S P d s P d P S P d S P d P S d P i i i i ) | ( ) ( max arg ) ( ) | ( ) ( max arg ) ( ) | ( ) ( max arg ) | ( max arg
Background image of page 4
Suppose we always reason from observed symptoms to diseases Characterize the boundaries Log(x) is monotonically increasing, so: Log of a product is…
Background image of page 5

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

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 18

Lect20 - Announcement HW4 on BNs due Tuesday Machine...

This preview shows document pages 1 - 6. Sign up to view the full document.

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