Fitting histogram with correlated systematic uncertainties

Newbie
1

Dear Experts,

I am a new user. I want to perform a fit of a histogram (with variable bin width) with correlated uncertainties among the bins with the data in Root. I am struggling to implement the correlation matrix (or covariance matrix) in my code.
Is there any sample code regarding this in the repository?

Thanks a lot in advance.

2

Hi @Srimoy_Bhattacharya,

Take a look at the Manual section Fitting histograms - ROOT.

Cheers,
J.

3

@jalopezg So, which example there covers the “correlated uncertainties among the bins” case?

4

Hi @jalopezg , I checked the link you shared.

I am not talking about the correlation among the fit parameters. I want to know how to incorporate “correlated uncertainties among the bins”.

Unfortunately, I could not find any discussion regarding this over there.

5

Sorry, I skipped over that part.

I am sure @moneta or @jonas can shed some light here.

Cheers,
J.

6

Hi,
We don’t have at the moment examples of fitting data where the points have correlated errors.
You need in this case to write yourself the Chi-square function using the correlation matrix.
We have however some example on fitting a user provided method, like this one fitting a 3D line to 3D points (ROOT: tutorials/fit/line3Dfit.C File Reference).

Best regards

Lorenzo