How to get polynomial (2nd order) excel trend–line coefficents in matlab?

If I use [p,S,mu] = polyfit(X,y,2), the coefficents I get are very different from the ones I find in excel. Should I use another function? How can I get the R squared?

Thank you in advance!

Answer 1

[Guillaume]

As documented, the [p, S, mu] output of polyfit centers and scales the returned polynomial, so it returns a different polynomial than the [p, S] ouput. If you want the same polynomial as Excel, use the [p, S] output.

As for the value that excel gives you, matlab does not give you that straight, but as explained by John here, you can calculate it:

[p, S] = polyfit(X, y, 2)  %if you want the same polynomial as excel.
r2 = 1 - (S.normr/norm(y - mean(y)))^2