I am trying to keep up with this discussion, perhaps there are bugs perhaps there are future enhancements.
You a referring to the thread I opened here http://communities.ptc.com/message/234933#234933 ? Not sure if I did something wrong there or not. But if not, then I would either expect a similar result as without units (at least if I use base units) or an error telling me, that regressions should not be done with units. I could image that there are reasons for better not using units here, but again I am not sure and so opened the discussion to collect other opinons.
But you lost me .. how did you come up with g(t,v). I have not seen this fitting function .. I dont think
I guess you have seen this fitting function already, but I sure should have better written it in a more convential way as the parameters would have a meaning if we do that and that can help to find guess values.
You are referring to
or in a later sheet
These are simply the sums of two or (the second) an arbitrary number of gaussians which are quite usual and useful functions to try for a fit in many situations. But I was surprised that I got that nearly perfect fit with 6 gaussians and also that slight changes in the guesses have that big impact on the result.
A gaussian is a function of the form
or may be written as
where y0 is the baseline offset, A is the total area under curve from the baseline, t0 is the center of the peak, w is something like 2 sigma, approximately 0.849 times the width of the peak at half height.
Richard had posted sums of gaussians from time to time in the past here and he uses
where h, w and t0 are controlling height, width and peak position.
The way of fitting multiple gaussians using the sum, matrix and minerr was stolen from Richard by me anyway.
I shouldn't had setup the function using meaningless coefficients, though.