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http://openclassroom.stanford.edu/MainFolder/DocumentPage.php?course=MachineLearning&doc=exercises/ex2/ex2.html
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Machine Learning Example 2
clc
clear
close all
x=load('ex2x.dat');
y=load('ex2y.dat');
figure
plot(x,y,'o')
ylabel('Height in meters')
xlabel('Age in years')
m = length(y); % store the size of data
x = [ ones(m,1),x]; %add a column to the x
%% linear regresion
theta = [0 0];
ss_old =theta;
ss_new = [inf inf];
alpha = 0.007;
while (abs(ss_new-ss_old)>0.0000000001)
ss_old = ss_new;
h_the = x*theta'; % prediction
theta(1)=theta(1)-alpha*(1/m).*sum(((h_the-y) .* x(:,1)));
theta(2)=theta(2)-alpha*(1/m).*sum(((h_the-y) .* x(:,2)));
ss_new=theta;
end
hold on
plot(x(:,2), x*theta', '-') % remember that x is now a matrix with 2 columns
% and the second column contains the time info
legend('Training data', 'Linear regression')
theta
[1 3.5]*theta'
[1 7]*theta'