Linear regression line in MATLAB scatter plot

Question

I am trying to get the residuals for the scatter plot of two variables. I could get the least squares linear regression line using lsline function of matlab. However, I want to get the residuals as well. How can I get this in matlab. For that I need to know the parameters a and b of the linear regression line

ax+b

Answer 1

Use the function polyfit to obtain the regression parameters. You can then evaluate the fitted values and calculate your residuals accordingly.

Basically polyfit performs least-squares regression for a specified degree N which, in your case will be 1 for straight line regression. The regression parameters are returned by the function and you can use the other function polyval to get the fitted values from the regression parameters

Answer 2

If you have the curve fitting toolbox, type cftool and press enter and the GUI will appear.

You can use this tool to find a linear polynomial fit for a given data set, as well as many other fits.