Need help with this code - linear regression/least squares

2016 9 27
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更新时间：2016 9 27
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the question and problem statement is on the pdf attachment. Tried my best with writing a code for it but I havn't taken matlab in 2 years so I'm extremely fuzzy. Down below is my first function statement but it didn't get included in the main code for some reason.
function CP2SmithTristen sumx=0; sumy=0; x= 1:5 ; y= [4, 7.1, 10.1, 12.5, 14.5]; end
function [a0,a1]=linear_regression(x,y)
for i = 1:5
n=length(x);
sumx = sumx + x(i);
sumy = sumy + y(i);
end
n = length(x);
a1=(n*(sumx*sumy)-sumx*sumy)/((n*sumx^2)-sumx^2);
a0=ym-(a1*xm);
xm = sumx/n
ym = sumy/n
end

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 采纳的回答

Massimo Zanetti
Massimo Zanetti 2016-9-27
编辑：Massimo Zanetti 2016-9-27

5 个投票

Hi Tristen. Here is the function for Ordinary Least Squares to linear regression
function [a0,a1]=linear_regression(x,y)
x=x(:);
y=y(:);
X=[x,ones(numel(x),1)];
a = (X'*X)\(X'*y);
a0=a(2);
a1=a(1);
end
So you can try it:
x= 1:5;
y= [4, 7.1, 10.1, 12.5, 14.5];
[a0,a1]=linear_regression(x,y);
plot(x,y,'r*'); %points
hold on;
plot(x,a0+a1*x,'b'); %line

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