I have a nonlienear model on the form

y=a*exp(b*x)+c*exp(b*d*x)+e*exp(b*d*d*x)

and I want to find a solution with the use of the Levenberg-Marquardt method.

Can anyone help me and tell me how to use mrqmin, mrqcof and so on to solve this problem?

I would like to specify my previous question.

When mrqcof calls the user-defined function (funcs), what is the expected results?

If I got it right, ymod is just the functions value at x for given unknowns in a[] and dyda is a vector with:

dydc
dydd
dyde

at a given x and for given unknowns in a[] (if c, d and e are my unknown variables).

Is this correct?