Adding data points on histogram and fit these points

ROOT
1

Hi, Rooters,

I was hoping to do this for a 2-D histogram, but I am taking a 1-D as an example which is presumably easier to explain: finding the points corresponding to 99.5% bin content of each bin, then fit these points. For instance, for a histogram has 3 bins: bin1 content = 100, bin2 content = 1000; bin3 content = 10,000.
I was hoping to: 1, adding these three points of 99.5, 995 and 9950 on the histogram (on-site);
2, fitting these three points (bin1, 99.5; bin2, 995; bin3 9950).

The attached screenshot was have done by my college on Python (for a 2-D histogram, not 1-D). I want to know wether this is achievable on ROOT ?
I know I can take the points out and fitting on a TGraph. Ideally, it would be nicer to do it on the same histogram, instead of doing it with a separate plot, as the screenshot shown.

Thanks.

Best,
Jun

example2D
example2D.png814×538 57.8 KB

Please provide the following information:

ROOT Version (e.g. 6.12/02):
6.08.02
Platform, compiler (e.g. CentOS 7.3, gcc6.2):
Mac OS High Sierra 10.13.4
Apple LLVM version 8.1.0 (clang-802.0.41)

2

If I understand correctly you would like to “add points” in your histograms ?
“Adding points” to an histogram is not very natural as an histogram is a “binned” object. You may consider make a new histogram with more bins but surely using a TGraph seems straighter path as the concept of “point” is really part of it.

3

Hi, Couet,

Thanks for looking at this.
You are right, I was hoping to add points on histograms.
If this is not a natural feature on ROOT, I will do it on a separate TGraph.

Thanks.

Best,
Jun

4

I do not think it is something ROOT specific. Histograms are binned objects being ROOT histograms or not.