To Calculate the slope

B= [ones(length(x1),1) x1(:)]\y1(:);   % Estimate Regression Parameters

yf = [ones(length(x1),1) x1(:)]*B;      % Calculate Regression Line
slope= B(2);
intercept = B(1);

 plot(x1,y1,'.b');

 plot (x1,yfaa,'r')

 text(-20,-25,['y = ', num2str(round(Baa(2)*100)/100), 'x'],'fontsize',20);

[Hana]

Sorry. I pressed enter without asking my question. I want to know for calculating regression line I should allocate an arrays of ones or zeros? I don't know which one is correct. and also 'y = ', num2str(round(Baa(2)*100)/100), is correct or I don't need to multiply and divide it by 100? Thanks

[Adam]

What is the question? You have just pasted some code in!

Answer 1

[Star Strider]

Using ones is correct. I create a design matrix and use it both for estimating the parameters and calculating the regression line afterwards. This involves some minor changes to your code:

DsnMtx = [ones(size(x(:)) x1(:)];
B = DsnMtx\y1(:);   % Estimate Regression Parameters
yf = DsnMtx*B;      % Calculate Regression Line

That is slightly more efficient, since you only need to calculate the design matrix once.

[Hana]

Thanks for the answer. I get a syntax error on DsnMtx = [ones(size(x(:)) x1(:)];

and is this line correct? text(0,17,['y = ', num2str(round(B(2)*100)/100),'x'],'fontsize',20);

Thanks

[Star Strider]

My pleasure.

The syntax error is due to a typographical error in my code. I forgot the ‘1’. It should be:

DsnMtx = [ones(size(x1(:)) x1(:)];

I would use the sprintf function instead:

text(0,17,sprintf('y = %.2f', x),'fontsize',20);

You might want to experiment with the 'VerticalAlignment' and 'HorizontalAlignment' name-value pairs as well.