hist039_TH2Poly_usa.C File Reference

Detailed Description

This tutorial illustrates how to create an histogram with polygonal bins (TH2Poly), fill it and draw it using the col option.

The initial data are stored in TMultiGraphs. They represent the USA map. Such histograms can be rendered in 3D using the option legogl.

The initial data have been downloaded from: http://www.maproom.psu.edu/dcw/ This database was developed in 1991/1992 and national boundaries reflect political reality as of that time.

 
void hist039_TH2Poly_usa()
{
   Int_t i, bin;
   const Int_t nx = 48;
   const char *states[nx] = {
      "alabama",      "arizona",      "arkansas",       "california",    "colorado",      "connecticut",   "delaware",
      "florida",      "georgia",      "idaho",          "illinois",      "indiana",       "iowa",          "kansas",
      "kentucky",     "louisiana",    "maine",          "maryland",      "massachusetts", "michigan",      "minnesota",
      "mississippi",  "missouri",     "montana",        "nebraska",      "nevada",        "new_hampshire", "new_jersey",
      "new_mexico",   "new_york",     "north_carolina", "north_dakota",  "ohio",          "oklahoma",      "oregon",
      "pennsylvania", "rhode_island", "south_carolina", "south_dakota",  "tennessee",     "texas",         "utah",
      "vermont",      "virginia",     "washington",     "west_virginia", "wisconsin",     "wyoming"};
   Double_t pop[nx] = {4708708,  6595778, 2889450,  36961664, 5024748, 3518288,  885122,  18537969, 9829211, 1545801,
                       12910409, 6423113, 3007856,  2818747,  4314113, 4492076,  1318301, 5699478,  6593587, 9969727,
                       5266214,  2951996, 5987580,  974989,   1796619, 2643085,  1324575, 8707739,  2009671, 19541453,
                       9380884,  646844,  11542645, 3687050,  3825657, 12604767, 1053209, 4561242,  812383,  6296254,
                       24782302, 2784572, 621760,   7882590,  6664195, 1819777,  5654774, 544270};
 
   TCanvas *usa = new TCanvas("USA", "USA");
   usa->ToggleEventStatus();
   Double_t lon1 = -130;
   Double_t lon2 = -65;
   Double_t lat1 = 24;
   Double_t lat2 = 50;
   TH2Poly *p = new TH2Poly("Lower48", "Lower 48 Population (2009);Latitude;Longitude", lon1, lon2, lat1, lat2);
 
   TFile::SetCacheFileDir(".");
   TFile *f = TFile::Open("http://root.cern/files/usa.root", "CACHEREAD");
 
   if (!f) {
      printf("Cannot access usa.root. Is internet working ?\n");
      return;
   }
 
   // Define the TH2Poly bins.
   TMultiGraph *mg;
   TKey *key;
   TIter nextkey(gDirectory->GetListOfKeys());
   while ((key = (TKey *)nextkey())) {
      TObject *obj = key->ReadObj();
      if (obj->InheritsFrom("TMultiGraph")) {
         mg = (TMultiGraph *)obj;
         bin = p->AddBin(mg);
      }
   }
 
   // Fill TH2Poly, with capital letters for the states names
   for (i = 0; i < nx; i++)
      p->Fill(states[i], pop[i]);
 
   gStyle->SetOptStat(0);
   p->Draw("colz textn");
 
   // Add the reference for the population
   TLatex pupulationRef(-128, 27, "#scale[.55]{#splitline{Source:}{http://eadiv.state.wy.us/pop/st-09est.htm}}");
   pupulationRef.DrawClone();
}

Date

February 2024

Author

Olivier Couet

Definition in file hist039_TH2Poly_usa.C.