(New User) How to project a 3D histogram along Y-axis

ROOT
1

This is what I’m trying to do:
-I have a 3D histogram that is in the 2D view with a regular xy-axis.
-I need to make a fairly small cut in the histogram that is parallel to the y-axis.
-Then I need to project the cut to the y-axis.
I appreciate the help. (I am using ROOT version 5.10)

2

A small macro showing what you are doing would help.

The help about TH3 projections can be found here:
root.cern.ch/root/html/TH3.html

Be careful that 5.10 is very old. Some functionalities described in the online doc might not exist in that version.

3

Here is the 3D histogram and its supplementary 2D histogram that I am working with: Thank you for your help.

4

You sent 2 images (jpeg files). We cannot help you a lot with that. As I said a small macro (a .C file) showing what you are doing will be more useful.

5

Ok, ignore the two images on my previous post.
-I used http://root.cern.ch/root/html/TH2.html#TH2:ProjectionY to assist me with this.

  • I made a TCutG object (the black box in the histogram below) and named it “cutg”.
  • I then entered in the following code: Ge2AT->ProjectionY("cutg",450,650,"[cutg]")
    -The terminal then displayed “(const class TH1D*)0xbe2aeb8”
  • I’m not sure what to do next, or if I am even approaching it the right way, but I want to project the boxed cut to the y-axis.

Thanks again for your help.

6

You can do:

TH1D *h1 = Ge2AT->ProjectionY("cutg",450,650,"[cutg]");
h1->Draw();
7

Thank you so much. I guess you don’t even need to manually draw the TCutG. Works great.