Description
Question 1 (30%)
Problem 2.13 from the textbook (included in the next page).
Question 2 (35%)
Write a function that generates a specified number of independent and identically distributed
samples paired with the class labels that generated these samples. Specifically, the data distribution
is a mixture of Gaussians with specified prior probabilities for each Gaussian class conditional pdf,
as well as respective mean vectors and covariance matrices. Generate and visualize data in the form
of scatter plots, with a color/marker based identification of the class label for each sample for each
of the following cases (using Matlab syntax for 2×2 matrices):
1. Number of samples = 400; class means [0,0]
T
and [3,3]
T
; class covariance matrices both set
to I; equal class priors.
2. All parameters same as (1), but both covariance matrices changed to [3,1; 1,0.8].
3. Number of samples = 400; class means[0,0]
T
and [2,2]
T
; class covariance matrices[2,0.5; 0.5,1]
and [2,−1.9;−1.9,5]; equal class priors.
4. Same (1), but prior for class priors are 0.05 and 0.95.
5. Same (2), but prior for class priors are 0.05 and 0.95.
6. Same (3), but prior for class priors are 0.05 and 0.95.
Make sure your plots include axis labels, titles, and data legends. Describe how your sampling
procedure works, using zero-mean identity-covariance Gaussian sample generators.
Additionally, for each of these datasets, use the maximum-a-priori (MAP) classification rule
(using full knowledge of the respective data pdfs) and produce inferred class labels for each data
samples. In accompanying visualizations, demonstrate scatter plots of the data for each case along
with their inferred (decision) labels. For each case, count the number of errors and estimate the
probability of error based on these counts.
Question 3 (35%)
For the datasets you generated in Question 2, implement and apply the Fisher Linear Discriminant Analysis classifier with the decision threshold for the linear discriminant score set to minimize
the smallest probability error you can achieve on the specific data sets generated for each case. Visualize the one-dimensional Fisher LDA discriminant scores and decision labels for each sample
in separate plots for each case. Note: We will soon discuss the principle of cross-validation that
dictates parameter selection and performance assessment must use independent datasets.
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2
