Administrivia Machine Learning Curve Fitting Coin Tossing

Administrivia - Background• Calculus:

E = mc2 ! !E!c

= 2mc

• Linear algebra:

Aui = "iui;!

!x(xTa) = a

• See PRML Appendix C• Probability:

p(X) =∑

Y

p(X, Y); p(x) =∫

p(x, y)dy; Ex[f ] =∫

p(x)f (x)dx

• See PRML Ch. 1.2, tutorial by Reza Friday Sept. 11 1-3pmT9204

It will be possible to refresh, but if you’venever seen these before this course will bevery difficult.

Administrivia Machine Learning Curve Fitting Coin Tossing

What is Machine Learning (ML)?

• Algorithms that automatically improve performancethrough experience

• Often this means define a model by hand, and use data tofit its parameters

Administrivia Machine Learning Curve Fitting Coin Tossing

Why ML?

• The real world is complex – difficult to hand-craft solutions.• ML is the preferred framework for applications in many

fields:• Computer Vision• Natural Language Processing, Speech Recognition• Robotics• . . .

Administrivia Machine Learning Curve Fitting Coin Tossing

Hand-written Digit Recognition

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Belongie et al. PAMI 2002

• Difficult to hand-craft rules about digits

Administrivia Machine Learning Curve Fitting Coin Tossing

Hand-written Digit Recognition

xi =

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ti = (0, 0, 0, 1, 0, 0, 0, 0, 0, 0)

• Represent input image as a vector xi " R784.• Suppose we have a target vector ti

• This is supervised learning• Discrete, finite label set: perhaps ti " {0, 1}10, a

classification problem• Given a training set {(x1, t1), . . . , (xN , tN)}, learning problem

is to construct a “good” function y(x) from these.• y : R784 # R10

Administrivia Machine Learning Curve Fitting Coin Tossing

Face Detection

Schneiderman and Kanade, IJCV 2002

• Classification problem• ti " {0, 1, 2}, non-face, frontal face, profile face.

Administrivia Machine Learning Curve Fitting Coin Tossing

Spam Detection

• Classification problem• ti " {0, 1}, non-spam, spam• xi counts of words, e.g. Viagra, stock, outperform,multi-bagger