TCut: 2-D gates around the central region of the plot

[thegame]

Hi all, I have plotted a Y:X plot with colz and found the centre of the plot is well in agreement with the prediction. however, around the centre, I have got a few data points which don’t match the expected correlation. Thus want to investigate further by applying 2D gates there and that’s where my problem arises. Can’t apply 2-D gates in a systematic way that automatically captures the data outside the central region of the attached plot (circled in RED) and eventually store them in a file or something. Any suggestions will be appreciated. Thanks!

[eguiraud]

Hi @thegame ,

if I understand correctly you want to extract the coordinates of data points that satisfy some constraints?

Some of that might be covered by ROOT: TCutG Class Reference – you can also access the bin contents of the TH2 manually of course, e.g. to zero-out the contents of the central bin to leave just the outer ones filled, and then continue the analysis from there.

Cheers,
Enrico

[couet]

You gates looks quite simple to program.According to your plot the middle part is enclose in a square defined by: -20 < x <20 and -20 < y < 20. Therefore you can make a loop identifying the 8 squares surrounding the central one:

    +---------------+---------------+---------------+
    |               |               |               |
    |      1        |       2       |       3       |
    |               |               |               | 
 20 +---------------+---------------+---------------+
    |               |               |               |
    |      4        |    centre     |       5       |
    |               |               |               |
-20 +---------------+---------------+---------------+
    |               |               |               |
    |      6        |       7       |       8       |
    |               |               |               |
    +---------------+---------------+---------------+
                   -20              20

Some (pseudo)code like the following one should be able to sort the various zones:

   int bin;
   double c, x,y;
   for (int i=1; i<=nbinx, i++) {
      for (int j=1; i<=nbiny, j++) {
         bin = h->GetBin(i,j);
         c = h->GetBinContent(bin);
         if (c) {
            x = h->GetXaxis()->GetBinCenter(bin);
            y = h->GetYaxis()->GetBinCenter(bin);
            if (x<-20 && y<-20) --> in zone 6
            if (x>=-20 && x<=20 and && y<-20) --> in zone 7
            if (x>20 && y<-20) --> in zone 8
            if (x<-20  && y>=-20 && y<=20) --> in zone 4
            if (x>=-20 && x <=20  && y>=-20 && y<=20) --> in center
            if (x>20 and && y>=-20 && y<=20) --> in zone 5
            if (x<-20 && y>20) --> in zone 1
            if (x>=-20 && x<=20 and && y>20) --> in zone 2
            if (x>20 && y>20) --> in zone 3
         }
      }
   }