EM CODE IN MATLAB with examples

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biao Peng
biao Peng 2020 年 11 月 7 日
I would like to know how EM matab code dealing with attached data to solve missing label problem.
see problem 1 as follows:
  • Save “hw3.mat” in your Matlab working directory.
  • In Matlab, type “load hw3.mat”
  • Then type “who”, you will find three matrices named “hw3_1”, “hw3_2_1” and “hw3_2_2”.
  • Each of these matrices has a size of 2×100, i.e. 2 rows and 100 columns. Each column is a 2-D observation vector.
Problem 1: The sample vectors in “hw3_1” are drawn from a Gaussian Mixture Model (GMM) with two mixtures, which can be expressed as
where x, µ1, µ2 are 2×1 vectors, and Σ1, Σ2 are 2×2 matrices, and ρ is the mixing parameter.
Use Expectation-Maximization (EM) algorithm to estimate the parameters µ1, µ2, Σ1, Σ2 and ρ.
Hint: Let the initial ρ0=0.5, and assume the first 50 samples are from p1(x) and the next 50 samples are from p2(x). Use Maximum Likelihood method (CPE646-4, page 19) to estimate the initial µ1, µ2, Σ1, Σ2
Problem 2: The sample vectors in “hw3_2_1” are from class ω1 and sample vectors in “hw3_2_2” are from class ω2
  1. Use Parzen window method to estimate the class conditional density functions p(x|ω1) and p(x|ω2) for every x in {-4:0.1:8, -4:0.1:8}; use “mesh” function in Matlab to plot the results; and then classify x=[1,-2]t based on the estimation. Let h1=2.
  1. Construct a Probabilistic Neural Network (PNN); and classify x=[1,-2]t. Let σ=0.2.

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