Need help with this code - linear regression/least squares

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

Answer 1

[Massimo Zanetti]

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