Using polyfit for linear regression

Hi guys, how do i get linear regression (p) of this X1 and Y1 values using polyfit?

I try but the X1 and Y1 keep changes back, expected i get like this graph in help window

[KSSV]

Try clear all and run the code.

[agung pratama]

Im sorry but its not working,

Do you think the code must be change?

Answer 1

[Bjorn Gustavsson]

Your code looks OK. Your problem might be that you expect a result identical to the figure from the documentation.

However, you ask for a linear fit in your call to polyfit - note the difference between your call and the call in the documentation!

your call:

p = polyfit(x,y,1);

Call in documentation:

p = polyfit(x,y,7);

You ask for a first-order polynomial, the call from the documentation is for a 7-order polynomial. That's the difference.

HTH

[agung pratama]

Yes i do that in purpose,i want first-order polynomial, so i change the code. My problem is how i change x1 and y1 value to get new p.