I have experimental data of an equation of type: y = a1*e^(b*x) where e is the exponential(antilog) for the y experimental data corresponding to x. My task is to fit the legendre polynomial of order 4, how i can do it. For this in the legendre equation what values i should use x or y or both. I have no idea that how to fit the legendre polynomial to experimental data. Please help anyone in this.