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Pattern Recognition and Machine Learning

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Presentation on theme: "Pattern Recognition and Machine Learning"— Presentation transcript:

1 Pattern Recognition and Machine Learning
Chapter 1: Introduction

2 Example Handwritten Digit Recognition

3 Polynomial Curve Fitting

4 Sum-of-Squares Error Function

5 0th Order Polynomial

6 1st Order Polynomial

7 3rd Order Polynomial

8 9th Order Polynomial

9 Over-fitting Root-Mean-Square (RMS) Error:

10 Polynomial Coefficients

11 Data Set Size: 9th Order Polynomial

12 Data Set Size: 9th Order Polynomial

13 Regularization Penalize large coefficient values

14 Regularization:

15 Regularization:

16 Regularization: vs.

17 Polynomial Coefficients

18 Probability Theory Apples and Oranges

19 Probability Theory Marginal Probability Conditional Probability
Joint Probability

20 Probability Theory Sum Rule Product Rule

21 The Rules of Probability
Sum Rule Product Rule

22 Bayes’ Theorem posterior  likelihood × prior

23 Probability Densities

24 Expectations Conditional Expectation (discrete)
Approximate Expectation (discrete and continuous)

25 Variances and Covariances

26 The Gaussian Distribution

27 Gaussian Mean and Variance

28 The Multivariate Gaussian

29 Gaussian Parameter Estimation
Likelihood function

30 Maximum (Log) Likelihood

31 Properties of and

32 Curve Fitting Re-visited

33 Maximum Likelihood Determine by minimizing sum-of-squares error,

34 Predictive Distribution

35 MAP: A Step towards Bayes
Determine by minimizing regularized sum-of-squares error,

36 Bayesian Curve Fitting

37 Bayesian Predictive Distribution

38 Model Selection Cross-Validation

39 Curse of Dimensionality

40 Curse of Dimensionality
Polynomial curve fitting, M = 3 Gaussian Densities in higher dimensions

41 Decision Theory Inference step Determine either or . Decision step For given x, determine optimal t.

42 Minimum Misclassification Rate

43 Minimum Expected Loss Example: classify medical images as ‘cancer’ or ‘normal’ Decision Truth

44 Minimum Expected Loss Regions are chosen to minimize

45 Reject Option

46 Why Separate Inference and Decision?
Minimizing risk (loss matrix may change over time) Reject option Unbalanced class priors Combining models

47 Decision Theory for Regression
Inference step Determine . Decision step For given x, make optimal prediction, y(x), for t. Loss function:

48 The Squared Loss Function

49 Generative vs Discriminative
Generative approach: Model Use Bayes’ theorem Discriminative approach: Model directly


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