SetOptFit and FixParameter

ROOT
1

Hello,

I have a specific problem for a paper that is going to publication. I have a data distribution that is fit to a Gaussian. The statistics box shows just the RMS of the data, and the mean and sigma of the fit. However, when we rounded to the correct number of sigdigs, the mean comes out “-0.0”, since the mean is just a smidgin on the negative side of zero. One of the reviewers of the draft paper didn’t like this, and so we thought to “FixParameter” the mean to 0.0 since it’s so close to zero. However, we’ve already set “v=1” in SetOptFit in order to suppress displaying the constant term, which is also fixed to the best value specifically for this reason.

So when you fix the mean at 0.0, the mean disappears from the stats box! But if you set v=0, then the constant term shows up too, which we don’t want.

Is there any way out of this dilemma?

Thanks,
-Phil D.

2

Can you post a small example reproducing this problem ?

3

I just haven’t got the time to gin up an example. I thought the problem was obvious from the ROOT documentation. So I hacked my own local ROOT installation, particularly THistPainter.cxx, so that it would skip putting the constant parameter into the stats box. Then I can force it to display “all” fit parameters and get what I want.

Regards,
-P

4

I could not reproduce what you described. That is why I asked you an example.