Lorentz2D Fit

This Wikipedia page has a description of a multivariate Lorentzian distribution (they call it Cauchy):

https://en.wikipedia.org/wiki/Cauchy_distribution#Multivariate_Cauchy_d…

Scroll down to the multivariate section. It says, "Note that in this example, even though there is no analogue to a covariance matrix, {\displaystyle x}x and {\displaystyle y}y are not statistically independent." So I don't know if that equation gives you what you need.

We have never tried to provide automatic guessing for user-defined fit functions. Those functions can be absolutely anything that has the form of an analytic function, so it's hard to know how we could do that. The auto-guessing for the built-in functions is the result of pains-taking hand coding specific to each of the fitting functions.

On the other hand, there may be a way for you to write something that guesses adequately for your particular function. If so, you can write a small function that automates the guessing and running of FuncFit for your situation.

Thanks, I used the function available on wiki and initialized the adjustment parameters with a wave containing the coefficients.

Would you be willing to post your fitting function code? Who knows, that might just get it included as a built-in for Igor 10 or something. No promises, but maybe.