Confidence intervals for combined fit


I am fitting 3 functions simultaneously with some common parameters, very similarly as in this tutorial: … Fit.C.html (only that I am fitting TGraphErrors instead of histograms).
The fit works fine, but when I try to get (and plot) confidence intervals for these 3 fitted functions, the code crashes every time.
I was trying to use similar procedures as in this tutorial: … als.C.html , using “(TVirtualFitter::GetFitter())->GetConfidenceIntervals”, but without any success. I think the problem is in telling the fitter for which function I want the confidence interval, because I am minimizing only 1 (i.e., combined) chi2.

If you have experience with this issue, I’d be thankful if you could help and tell me how to get confidence intervals for fitted functions when using combined fit.

Many thanks!

I am also attempting to do the same task. I have 4 TGraphs with one parameter common to all. I would like to plot the confidence bounds of each fit, except that I run into the same issue around the fit result being generated from the global fit.