Count points inside a TGraph curve

[david90]

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Hello everyone,

I have a contour level curve in a TGraph object, also I have 100 points which coordinates are stored in x and y arrays, is there a way to count how many points are within this contour and how many are outside of it using ROOT?. Any suggestion would be really appreciate it.

Thanks,

David.

ROOT Version: 6.12/06

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[dastudillo]

You can create a graphical cut from the contour points and then check the other points with IsInside:

How to Count Events within an Odd-Shaped Region?

I don’t know if there is a dedicated function, but what you can do is: 1 - define the closed polygon as a TCutg (https://root.cern/doc/master/classTCutG.html) 2 - loop over the histogram bins, get the bin centres and use IsInside() to check whether the point is inside the area; if it is, get its contents and add them. for (Int_t ix=1; ix<Nbx; ++ix) { for (Int_t iy=1; iy<Nby; ++iy) { x = h->GetXaxis()->GetBinCenter(ix); y = h->GetYaxis()->GetBinCenter(iy); if (cutg->IsI…

[david90]

@dastudillo, Thanks!, this is what I was looking for.