haxis.cxx

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/// \file
/// \ingroup tutorial_webcanv
/// \notebook -js
/// Swap X/Y axes drawing and use to draw TH1 as bar and as markers.
///
/// Option "haxisg;y+" draw histogram axis as for "hbar" plus allow to draw grids plus draw Y labels on other side
/// Option "bar,base0,same" draws histogram as bars with 0 as reference value
/// Option "P,same" draws histogram as markers
/// Macro also shows how frame margins can be configured and poly-line drawing like filled arrow can be
/// placed relative to frame.
///
/// Functionality available only in web-based graphics
///
/// \macro_image (tcanvas_js)
/// \macro_code
///
/// \author Sergey Linev
 
void haxis()
{
   std::vector<double> negative = {-5, -7, -3, -1};
   std::vector<double> positive = {2, 15, 2, 10};
   std::vector<std::string> labels = {"Category 1", "Category 2", "Category 3", "Category 4"};
 
   // position of frame
   double frame_left = 0.15, frame_right = 0.9, frame_top = 0.8, frame_bottom = 0.05;
 
   auto nbins = negative.size();
 
   auto hmain = new TH1D("hmain", "title", nbins, 0, nbins);
   hmain->SetMarkerSize(3);
   hmain->SetMarkerStyle(33);
   hmain->SetMarkerColor(kBlue);
 
   auto hpos = new TH1D("hpos", "title", nbins, 0, nbins);
   hpos->SetFillColor(kRed);
   hpos->SetBarOffset(0.2);
   hpos->SetBarWidth(0.6);
 
   auto hneg = new TH1D("hneg", "title", nbins, 0, nbins);
   hneg->SetFillColor(kGreen);
   hneg->SetBarOffset(0.2);
   hneg->SetBarWidth(0.6);
 
   double vmin = 0, vmax = 0;
 
   for (unsigned n = 0; n < nbins; n++) {
      hmain->SetBinContent(n + 1, negative[n] + positive[n]);
      hpos->SetBinContent(n + 1, positive[n]);
      hneg->SetBinContent(n + 1, negative[n]);
      if (negative[n] < vmin)
         vmin = negative[n];
      if (positive[n] > vmax)
         vmax = positive[n];
   }
 
   double scale_min = (vmin - (vmax - vmin) * 0.1), scale_max = (vmax + (vmax - vmin) * 0.1),
          frame_0 = (0 - scale_min) / (scale_max - scale_min) * (frame_right - frame_left) + frame_left;
 
   auto haxis = new TH1D("haxis", "title", nbins, 0, nbins);
   haxis->SetMinimum(scale_min);
   haxis->SetMaximum(scale_max);
   haxis->SetStats(false);
   for (unsigned n = 0; n < nbins; n++)
      haxis->GetXaxis()->SetBinLabel(n + 1, labels[n].c_str());
   haxis->GetXaxis()->SetTickSize(0);
   haxis->GetXaxis()->SetLabelSize(0.07);
   haxis->GetXaxis()->SetLabelOffset(0.02);
 
   auto c1 = new TCanvas("chaxis", "title", 1500, 800);
 
   if (!gROOT->IsBatch() && !c1->IsWeb())
      ::Warning("haxis.cxx", "macro may not work without enabling web-based canvas");
 
   c1->SetLeftMargin(frame_left);
   c1->SetRightMargin(1 - frame_right);
   c1->SetTopMargin(1 - frame_top);
   c1->SetBottomMargin(frame_bottom);
   c1->SetGridy(1);
   // c1->SetGridx(1);
 
   c1->Add(haxis, "haxisg;y+"); // swap x/y axis, let draw grids, y on top
 
   c1->Add(hpos, "bar,base0,same"); // draw as bar, 0 as base, same
   c1->Add(hneg, "bar,base0,same"); // draw as bar, 0 as base, same
   c1->Add(hmain, "P,same");        // draw as marker, also text and line supported, same
 
   TLatex *title = new TLatex((frame_left + frame_right) * 0.5, 0.96, "Example of haxis with overlayed histograms");
   title->SetNDC(true);
   title->SetTextAlign(22);
   title->SetTextSize(0.08);
   title->SetTextColor(kBlue);
   c1->Add(title);
 
   auto add_arrow = [&](bool left_side, const char *txt) {
      double x1 = left_side ? frame_0 - 0.02 : frame_0 + 0.02, x2 = left_side ? frame_left + 0.05 : frame_right - 0.05,
             x3 = left_side ? frame_left + 0.03 : frame_right - 0.03, y0 = frame_top + 0.08, wy = 0.02;
 
      std::vector<double> xpos = {x1, x2, x2, x3, x2, x2, x1, x1};
      std::vector<double> ypos = {y0 + wy, y0 + wy, y0 + wy * 1.5, y0, y0 - wy * 1.5, y0 - wy, y0 - wy, y0 + wy};
      TPolyLine *pleft = new TPolyLine(xpos.size(), xpos.data(), ypos.data());
      pleft->SetFillColor(left_side ? kGreen : kRed);
      pleft->SetNDC();
      c1->Add(pleft, "f");
 
      TLatex *l = new TLatex(left_side ? x1 - 0.03 : x1 + 0.03, y0, txt);
      l->SetNDC(true);
      l->SetTextAlign(left_side ? 32 : 12);
      l->SetTextSize(0.03);
      l->SetTextColor(kWhite);
      c1->Add(l);
   };
 
   add_arrow(true, "Reduction");
 
   add_arrow(false, "Increase");
 
   auto box = new TBox(0.2, 6, 0.8, 14);
   box->SetFillColor(kCyan);
   box->SetLineColor(kRed);
   box->SetLineWidth(3);
   // use "frame" option to embed box into frame, "l" for line drawing
   c1->Add(box, "l,frame");
 
   auto l1 = new TLatex(0.5, 10, "Text inside frame");
   l1->SetTextAlign(22);
   l1->SetTextSize(0.04);
   l1->SetTextColor(kMagenta);
   // use "frame" option to embed text into frame
   c1->Add(l1, "frame");
}