search for: gradint

....st, control=try.control, trace=T) The data is from experiments and the pattern of data is scatter quite a bit. I want to find the best fit coefficients (a,b,c,d,e,f,g) for the data. I have two different sets of initial values for try. But in both cases I got error message of "singular gradint" What can I do for this error? Is there any other nonlinear regression model I can try? This problem is kind of emergency. I really hope someone can help me out. Any comment is appreciated. Thanks a lot. Niner ----------------------------------------------- Yi-Min Huang Civil & En...