Origin Ver. and Service Release (Select Help-->About Origin): Operating System: Origin 8.0 G SR 6 I want to make a nonlinear fit with a user function in Origin 8.0. It doesn`t works. Same data, same function and Origin 6.0 and it works! In my opinion I have a problem in 8.0 with the input of the initial values. The program dont want such values like 6,9 or 0,8. If I take 6.9 or so it also doesn`t work. Only values like 6 or 80 will be accepted. Who can help me?