How to define histograms?
ROOT provides you with 3-d histograms as well. TH1D *h1 = new TH1D(“h1”, “histogram title”, 100, 0., 10.); TH2D *h2 = new TH2D(“h2”, “histogram title”, 100, 0., 10., 18, 0., 180.); TH3D *h3 = new TH3D(“h3″, histogram title”, 100, 0., 10., 18, 0., 180., 10, 0., 1.); What Options are there for drawing? Many of these options are the same like in PAW: h2->Draw(“text”); h2->Draw(“col”), h2->Draw(“colz”); h2->Draw(“box”); h2->Draw(“surf”); A complete list is available in the official documentation. How to overlay two histograms h1a->Draw(); h1b->Draw(“same”); How to copy a histogram TH1D hcopy(*h1); // assuming h1 is a pointer to a TH1D How to get Poissonian errors in an efficiency plot heff->Divide(hgood, hall, 1., 1., “b”); // assuming you have three histograms called hall, hgood, and heff How to get a profile histogram from a 2-d histogram Tprofile *px = h2->ProfileX(“px”, 0, 9); // where firstYbin = 0 and lastYbin = 9 px->Draw(); Tprofile *py = h2->ProfileY(“py”, 0, 9); // where firstXbi
