My problem is to find parameters to fit experimental curve (about 140 experimental points) with known function. BUT: this function is very complicated and has as much as ~50 parameters. So there is no possibility to calculate its gradient symbolically.
So the question is:
1) is there in Mathematica a way for automatic gradient calculation;
2) is there a possibility to fix some parameters;
3) and finally it would be greate if Mathematica is able to plot this function while finding parameters to let me check the progress of the calculations.
Thanks in advance to everybody who pays attention to my reply.