I'm seeing a discrepency between the coefficients obtained via MATLAB's fit function using the fitType power1 and the coefficients provided with the same data using two other stats packages, one of which is Excel. The other is JMP, which agrees with Excel. So, I'm thinking the Excel and JMP values are likely correct. Here a simple data set:
x = [1 2 3 4 5]y = [9.58 10.90 12.56 13.41 14.33]
Using MATLAB, I get…
f = fit(x',y','power1')f =General model Power1:f(x) = a*x^bCoefficients (with 95% confidence bounds):a = 9.384 (8.774, 9.994)b = 0.2592 (0.206, 0.3125)
Using the same data and a power fit, the a and b coefficients with Excel and JMP are different, however. They both give
a = 9.4293b = 0.9871
Any idea what might be causing this discrepency?