gaus class

This commit is contained in:
Michael Zhang 2023-10-07 22:42:35 -05:00
parent 5ff27d91f8
commit 063966d730
3 changed files with 120 additions and 0 deletions

35
gauss_class/gauss2d.m Normal file
View file

@ -0,0 +1,35 @@
% CSCI 5521 Introduction to Machine Learning
% Rui Kuang
% Demonstration of 2-D Gaussians
%Try Sigma = [0.5, 0;0, 0.5];Sigma = [0.7, 0;0, 0.3];Sigma = [0.7, 0.2;0.2, 0.3]
mu = [0 0];
Sigma = [0.7, 0.2;0.2, 0.3];
x1 = -3:.2:3; x2 = -3:.2:3;
[X1,X2] = meshgrid(x1,x2);
%pdf
F = mvnpdf([X1(:) X2(:)],mu,Sigma);
F = reshape(F,length(x2),length(x1));
subplot(1,2,1);
surf(x1,x2,F);
caxis([min(F(:))-.5*range(F(:)),max(F(:))]);
axis([-3 3 -3 3 0 .4])
xlabel('x1'); ylabel('x2'); zlabel('Probability Density');
subplot(1,2,2);
contour(x1,x2,F,[.0001 .001 .01 .05:.1:.95 .99 .999 .9999],'ShowText','on');
%contour
figure
i=1;
for rho = -0.8:0.4:0.8
Sigma(1,2)=rho*sqrt(Sigma(1,1)*Sigma(2,2));
Sigma(2,1)=Sigma(1,2);
F = mvnpdf([X1(:) X2(:)],mu,Sigma);
F = reshape(F,length(x2),length(x1));
subplot(1,5,i);
i=i+1;
contour(x1,x2,F,[.0001 .001 .01 .05:.1:.95 .99 .999 .9999]);
title (sprintf('rho = %f',rho));
xlabel('x1'); ylabel('x2');
end

View file

@ -0,0 +1,33 @@
% CSCI 5521 Introduction to Machine Learning
% Rui Kuang
% Demonstration of Classification by 1-D Gaussians
%mean and standard deviation of class blue
mu1 = -2;sd1 = 2;
%mean and standard deviation of class red
mu2 = 2;sd2 = 4;
%generate x-axis
sd = max(sd1,sd2);
ix = -6*sd-1:1e-1:6*sd+1; %covers more than 99% of the curve
iy1 = pdf('normal', ix, mu1, sd1);
iy2 = pdf('normal', ix, mu2, sd2);
subplot(1,2,1);
plot(ix,iy1,'b'); hold on;
plot(ix,iy2,'r');
title('PDF P(X)');
%prior
p1=0.8;
p2=1-p1;
%calculate the posteriors
iy1_n = p1*iy1 ./ (p1*iy1+p2*iy2);
iy2_n = p2*iy2 ./ (p1*iy1+p2*iy2);
subplot(1,2,2);
plot(ix,iy1_n,'b'); hold on;
plot(ix,iy2_n,'r');
title('Posteriors P(C | x)');

View file

@ -0,0 +1,52 @@
% CSCI 5521 Introduction to Machine Learning
% Rui Kuang
% Demonstration of Classification by 2-D Gaussians
mu1 = [-1 -1];
mu2 = [1 1];
% Equal diagnoal covariance matrix
Sigma1 = [1 0; 0 1];
Sigma2 = [1 0; 0 1];
% Diagnoal covariance matrix
% Sigma1 = [1 0; 0 0.5];
% Sigma2 = [1 0; 0 0.5];
% Shared covariance matrix
% Sigma1 = [1 0.3; 0.3 0.5];
% Sigma2 = [1 0.3; 0.3 0.5];
x1 = -10:.1:10; x2 = -10:.1:10;
% covariance matrix (increase the range for visualization)
% Sigma1 = [1 0.1; 0.1 0.5];
% Sigma2 = [0.5 0.3; 0.3 1];
% x1 = -40:.1:40; x2 = -40:.1:40;
[X1,X2] = meshgrid(x1,x2);
%pdf1
F1 = mvnpdf([X1(:) X2(:)],mu1,Sigma1);
F1 = reshape(F1,length(x2),length(x1));
subplot(1,2,1);
surf(x1,x2,F1); hold on;
%pdf2
F2 = mvnpdf([X1(:) X2(:)],mu2,Sigma2);
F2 = reshape(F2,length(x2),length(x1));
surf(x1,x2,F2);
caxis([min(F2(:))-.5*range(F2(:)),max(F2(:))]);
axis([-4 4 -4 4 0 .4])
xlabel('x1'); ylabel('x2'); zlabel('Probability Density');
%decosopm boundary
%F1 = mvnpdf([X1(:) X2(:)],mu1,Sigma1);
%F1 = reshape(F1,length(x2),length(x1));
%F2 = mvnpdf([X1(:) X2(:)],mu2,Sigma2);
%F2 = reshape(F2,length(x2),length(x1));
cmp = F1 > F2;
subplot(1,2,2);
imagesc(X1(:),X2(:),cmp);
xlabel('x1'); ylabel('x2');