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June 1 2018
4. Non-seperable Data
PLA: simple to implement, fast, works in any dimension
Assumes linear seperable D to halt; not fully sure how long halting takes (不知道是否线性可分:可能不会停下; 不知道什么时候才会停下)
Learning with Noisy Data : Line with Noise Tolerance
Pocket Algorithm: Modify PLA by keeping best weights in pocket
Since we do no know whether D is linear seperable in advance, we may decide to just go with pocket instead of PLA.
When D is linear seperable:
pocket on D is slower than PLA for two reasons:
1. pocket要花时间存起来weights
2. 对于每一条线,pocket需要检查所有的点的误差
Week 3 Types of Learning
1. Learning with different Output Space
是非题(二元分类):
1 binary classification
2 multiclass classification
3 regression
4 structured learning
2. Learning with different data label
Supervised: Coin Recognition Revisited
Unsupervised: Coin Recognition without yn
unsupervised learning: diverse, with possibly very different performance goals
Semi-supervised: Coin Recognition with Some y n
Other Semi-supervised Learning Problems
• face images with a few labeled ⇒ face identifier (Facebook)
• medicine data with a few labeled ⇒ medicine effect predictor
semi-supervised learning: leverage unlabeled data to avoid ‘expensive’ labeling
Reinforcement Learning
Other Reinforcement Learning Problems Using (x, ỹ , goodness)
• (customer, ad choice, ad click earning) ⇒ ad system
• (cards, strategy, winning amount) ⇒ black jack agent
Learning with Different Data Label y n
• supervised: all y n
• unsupervised: no y n
• semi-supervised: some y n
• reinforcement: implicit y n by goodness( ỹ n )
• . . . and more!!
3. learning with different protocol
Batch Learning: Coin Recognition Revisited
batch supervised multiclass classification: learn from all known data
• batch of (email, spam?) ⇒ spam filter
• batch of (patient, cancer) ⇒ cancer classifier
• batch of patient data ⇒ group of patients
batch learning: a very common protocol
• batch spam filter: learn with known (email, spam?) pairs, and predict with fixed g
• online spam filter, which sequentially:
1 observe an email x t
2 predict spam status with current g t (x t )
3 receive ‘desired label’ y t from user, and then update g t with (x t , y t )
Learning with Different Protocol f ⇒ (x n , y n )
• batch: all known data unknown target function
• online: sequential (passive) data
• active: strategically-observed data
• . . . and more!!
4. learning with different input space
More on Concrete Features
• (size, mass) for coin classification
• customer info for credit approval
• patient info for cancer diagnosis
• often including ‘human intelligence’ on the learning task
concrete features: the ‘easy’ ones for ML
Raw Features: Digit Recognition Problem
• image pixels, speech signal, etc.
raw features: often need human or machines to convert to concrete ones
Abstract Features: Rating Prediction Problem
Rating Prediction Problem (KDDCup 2011)
• given previous (userid, itemid, rating) tuples, predict the rating that some userid would give to itemid?
• a regression problem with Y ⊆ R as rating and X ⊆ N × N as (userid, itemid)
• ‘no physical meaning’; thus even more difficult for ML Other Problems with Abstract Features
• student ID in online tutoring system (KDDCup 2010)
• advertisement ID in online ad system |
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