Need suggestion on how to highlight the 2D histogram plot after cut condition

[Divyang]

Hello,

I am new to ROOT and I need to highlight the portion of the 2D histogram after applying the cut condition.

I am creating two different plots: 1) before (left), and 2) after (right) applying the cut condition (see image). I want to plot these two plots on the same canvas and want to highlight the cut region.

Any suggestion on how can I do that. I think it would be better if I use a different colormap for the cut region, but I am not sure how to do that.

Here is the pseudo-code for what I am doing.

h = new TH2F("h", "h", 225, -200, 250, 225, -200, 250);
hcut = new TH2F("hcut", "hcut", 225, -200, 250, 225, -200, 250);

tree -> Draw( Form("y:x >> h", "", "colz"); // no cut condition

// different canvas
tree -> Draw( Form("y:x >> hcut", "cut condition form 'z' variable", "colz"); // cut condition applied

Any suggestion would be a great help for me.

Thanks,
Divyang.

[dastudillo]

https://root.cern/doc/v610/classTHistPainter.html#HP14
Search for the example with the text “Example of col plots with option SAME”. You can fill a second histogram (e.g. hcut2) with the entries that get cut out (using the opposite condition as for hcut), then scale this second histogram (or use SetBinContent to give all of its bins one same value, i.e. one same colour when plotted) so that its values (colours) are different from hcut, either lower than the ninimum or higher than the maximum, and plot it (hcut2) with SAME after plotting hcut; you may have to adjust the minimum or maximum of hcut so the colours are clearly different. E.g. if the maximum of hcut is 2.5x10^3, you could fill hcut2 with 4x10^3 (play with the values!) and then do hcut->SetMaximum(4*10e3)…

[dastudillo]

An alternative method:

TGraph2D contour with exclusion band

Dear experts, I have a TGraph2D drawn in cont4z option. Then I want to superimpose another TGraph2D on the same pad to use one of its contours as the exclusion limit for the first plot. I know how to put them on two pads, making the second pad transparent and so on. However, The second TGraph2D is a complicated 2D graph. I have limited the number of contours to 2 by doing g->GetHistogram()->SetContour(2) to get the first contour. This is fine and it works by showing only one contour superim…

You can get a contour plot with the CONT option.