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Reference Guide
th2polyUSA.C File Reference

Detailed Description

View in nbviewer Open in SWAN 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 th2polyUSA()
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");
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 *f = TFile::Open("http://root.cern.ch/files/usa.root", "CACHEREAD");
if (!f) {
printf("Cannot access usa.root. Is internet working ?\n");
// Define the TH2Poly bins.
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.
for (i=0; i<nx; i++) p->Fill(states[i], pop[i]);
p->Draw("colz textn");
#define f(i)
Definition: RSha256.hxx:104
int Int_t
Definition: RtypesCore.h:43
double Double_t
Definition: RtypesCore.h:57
#define gDirectory
Definition: TDirectory.h:229
R__EXTERN TStyle * gStyle
Definition: TStyle.h:410
The Canvas class.
Definition: TCanvas.h:27
virtual void ToggleEventStatus()
Toggle event statusbar.
Definition: TCanvas.cxx:2375
A ROOT file is a suite of consecutive data records (TKey instances) with a well defined format.
Definition: TFile.h:53
static Bool_t SetCacheFileDir(ROOT::Internal::TStringView cacheDir, Bool_t operateDisconnected=kTRUE, Bool_t forceCacheread=kFALSE)
Definition: TFile.h:323
static TFile * Open(const char *name, Option_t *option="", const char *ftitle="", Int_t compress=ROOT::RCompressionSetting::EDefaults::kUseCompiledDefault, Int_t netopt=0)
Create / open a file.
Definition: TFile.cxx:3942
virtual void Draw(Option_t *option="")
Draw this histogram with options.
Definition: TH1.cxx:2998
2D Histogram with Polygonal Bins
Definition: TH2Poly.h:66
virtual Int_t Fill(Double_t x, Double_t y)
Increment the bin containing (x,y) by 1.
Definition: TH2Poly.cxx:589
virtual Int_t AddBin(TObject *poly)
Adds a new bin to the histogram.
Definition: TH2Poly.cxx:222
Book space in a file, create I/O buffers, to fill them, (un)compress them.
Definition: TKey.h:28
virtual TObject * ReadObj()
To read a TObject* from the file.
Definition: TKey.cxx:738
A TMultiGraph is a collection of TGraph (or derived) objects.
Definition: TMultiGraph.h:36
Mother of all ROOT objects.
Definition: TObject.h:37
virtual Bool_t InheritsFrom(const char *classname) const
Returns kTRUE if object inherits from class "classname".
Definition: TObject.cxx:443
void SetOptStat(Int_t stat=1)
The type of information printed in the histogram statistics box can be selected via the parameter mod...
Definition: TStyle.cxx:1590
static constexpr double mg
Olivier Couet

Definition in file th2polyUSA.C.