Th 2Poly U S A

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.

Author: Olivier Couet
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Thursday, May 19, 2022 at 08:17 AM.

In [1]:
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("USA","USA Population",lon1,lon2,lat1,lat2);

TFile::SetCacheFileDir(".");
TFile *f = TFile::Open("http://root.cern.ch/files/usa.root", "CACHEREAD");

if (!f) {
   printf("Cannot access usa.root. Is internet working ?\n");
   return;
}

[TFile::Cp] Total 0.95 MB	|====================| 100.00 % [74.4 MB/s]
Info in <TFile::OpenFromCache>: using local cache copy of http://root.cern.ch/files/usa.root [./files/usa.root]

Define the th2poly bins.

In [2]:
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.

In [3]:
for (i=0; i<nx; i++) p->Fill(states[i], pop[i]);

gStyle->SetOptStat(11);
p->Draw("colz textn");

Draw all canvases

In [4]:
%jsroot on
gROOT->GetListOfCanvases()->Draw()