The smaller the sum of these squared figures, the better the function fits the data points in the set. Nonlinear regression uses logarithmic functions, trigonometric functions, exponential ...

the log link function and its inverse could be defined with the FWDLINK and INVLINK statements. fwdlink link = log(_MEAN_); invlink ilink = exp(_XBETA_); This code is for illustration, and it works ...