Root Tips (Memo for me)

Web pages

• The ROOT System Home Page
• http://root.cern.ch/root/html/
  
• ROOT Tutorial
• The root primer page
  
• Root Education at Fermilab

• My ROOT Libraries (w3.C, mkntpl.C...)
  

Misc.

To run (csh/tcsh)

> setenv ROOTSYS /usr/local/root
> setenv LD_LIBRARY_PATH $ROOTSYS/lib:$LD_LIBRARY_PATH
> setenv PATH $ROOTSYS/bin:$PATH
> root

To exit from root

ROOT> .q

 ~/.rootrc, rootlogon.C, rootlogoff.C

ROOT> .h

> [file] output redirect
2> [file] error redirect
?, .help help
.x evaluate {} in a file
.X execute function in a file.
".X ex.c" means to execute function "ex" in ex.C.
.L load file
.g show global variable

Coordinate System

1 +-------------+ ( X1, Y1, X2, Y2 )
  |             |
Y |             |
  |             |
0 +-------------+
  0      X      1

color

How to make frame transparent when print out.

gStyle->SetStatColor(0);
gStyle->SetTitleColor(0);
gStyle->SetCanvasColor(0);
gStyle->SetPadColor(0);
gStyle->SetPadBorderMode(0);
gStyle->SetCanvasBorderMode(0);
gStyle->SetFrameBorderMode(0);

Make eps file

c1->Print("filename.eps", "eps");

TH1F

• hpx = new TH1F("hpx","This is the px distribution",100,-4,4);
• Reset();   // clear all contents
  
• GetNbinsX()
• SetStats(kFALSE|kTRUE)  # if display statistics
• gStyle->SetOptFit(1111) # prob chi-sq/dof errors values 
  
• SetFillColor(color), SetLineColor(color)
• GetBinContent(1..nbin)
• SetBinContent(1..nbin, float?) # float seems to work well.
• FindBin(x)  # Return bin number corresponding to x (0.. underflow, NBIN+1.. overflow)
• GetBinCenter(1..nbin), GetBinLowEdge(1..nbin)  # x on x-axis corresponding to given bin number
  
• Draw("option")
• "same" : same as option s of PAW
• "e1p" : error bar, ?, polymark?
• DrawCopy("option") # You want to use this instead of Draw
• GetXaxis()->GetXmin() # GetXaxis return TAxis* object.
• ->GetXmax()
• ->SetTitle("title")
• SetTitle("title") # if "", then No title
• SetXTitle("x axis label")
  
• GetMaximum(), SetMaximum(Float_t)
•    ex.) hp11->SetMaximum(TMath::Max(hp11->GetMaximum(), hp12->GetMaximum())*1.05);
  
• SetTitleSize( Float_t size, "Y" )
• SetLabelSize( Float_t size, "X" ) -> number around x(y)-axis
• fArray[1..nbin] # can access bin content as an array
• Fill( x-value ) # will return bin number
• Fill(Axis_t x, Stat_t w)
  
• GetEntries()
• GetMean()

• Fit

  hist->Fit("gaus", "Q");
  TF1 *fit= hist->GetFunction("gaus");
  float mean=fit->GetParameter(1);
  float sigma=fit->GetParameter(2);

• Logscale
• (TCanvas*)c1 -> SetLogy(1); Linear scale: SetLogy(0)
• GetLogy();  Return true if Pad is set to Logy(1).
  
• Grid
• (TCanvas*)c1->SetGrid(1,1); grid off -> SetGrid(0,0);
• Operate
• h1->Add(h2, c2) : h1=h1+c2*h2
• h3->Add(h1, h2, c1, c2) : h3=c1*h1+c2*h2 : Can use if h3=h1 or h2?
• h1->Divide(h2) : h1=h1/h2
• h1->Multiply(h2) : h1=h1*h2
  

 TH2F

• TH2F* hpx = new TH2F("h","test",6,0,6, 12,0,12);
• hpx->SetBinContent(Int_t binx, Int_t biny, Stat_t content);
• 1..nbinx, 1..nbiny
• gStyle->SetPalette(1);
• hpx->DrawCopy("colz");

TNtuple

• ntuple = new TNtuple("ntuple", "Demo", "px:py:pz:random:i");
• Get("directory") -> (TNtuple*)f->Get("dir/path?")
• Draw("py:px", "condition", "same" )

How to `manual' loop

1. N=GetEntries()
2. GetEvent( 0..N-1 ) =(alias?) GetEntry( 0..N-1 )
3. n=GetNvar()
4. GetArgs()[ 0..n-1 ]

nt->Print()
Br 0 :var : x/F:y/F ...

============================================================sample========
ana(char* fname)
{
  TFile* f = new TFile(fname);
  // f->ls() will help you find the path name.
  TNtuple* ntpl = (TNtuple*)f->Get("ntuple");

  // How to `manual' loop
  Int_t n=ntpl->GetEntries();

  // ntpl->Print() will help you find what variables are cotained.
  Float_t p, thb1, thb2, phb2, thd1, thd2;
  ntpl->SetBranchAddress("v01", &p);
  ntpl->SetBranchAddress("v02", &thb1);
  ntpl->SetBranchAddress("v03", &thb2);
  ntpl->SetBranchAddress("v04", &phb2);
  ntpl->SetBranchAddress("v05", &thd1);
  ntpl->SetBranchAddress("v05", &thd2);

  // main loop
  for( Int_t idx=0; idx<10; ++idx ) {
    ntpl->GetEntry( idx );
    cout << p << " " << thb1 << " " << thb2 << endl;
  }

  f.Close();
}
// EOF
============================================================sample========

Filling to a histogram

TH1F* hp = new TH1F("hp", "hoge", 50, 0.0, 10.0);
nt->Draw("pathlength>>hp","pathlength>0");
nt->Draw("pathlength>>hp(50, 0.0, 10.0)","pathlength>0");

TCanvas, TPad

• TCanvas* c1=new TCanvas( "c1", "HOGE", 700, 500);
• TPad* pad1 = new TPad("pad1","The pad",0.03,0.62,0.50,0.92,21);
• Clear()
• ls()
-> after TH1F* hp->Draw()
• TPad fXlowNDC...
• GetPrimitive("title") .... will return TPaveText* object
• SetRightMargin(0.05)
• Left/Bottom/Top

How to obtain the objects on the Canvas:

• TList* l=c1->GetListOfPrimitives();
• l->Print();
• TLine X1=0.026210 Y1=0.913690 X2=0.691532 Y2=0.577381
• Ellipse: X1= 0.385081 Y1=0.462798 R1=0.233871 R2=0.102679
• TEllipse* e1=l->At(1);
  

How to make Staticstics box bigger:  <-- Obsolete!

c1 = new TCanvas( "c1", "HOGE", 500, 700);
pad1 = new TPad("pad1","The pad",0.03,0.62,0.50,0.92,21)
pad2 = new TPad("pad2","The pad",0.03,0.32,0.50,0.60,20)
pad1->Draw()
pad2->Draw()
pad1->cd()
hpx = new TH1F("hpx","This is the px distribution",100,-4,4)
hpx->Draw()
pad2->cd()
hpy = new TH1F("hpy","This is the py distribution",100,-4,4)
hpy->Draw()

TPaveStats *stat1=(TPaveStats*)pad1->GetPrimitive("stats")
// 'pad1->ls()' tells what objects are in pad1.
// 'stats', 'title' will be available as an argument
stat1->SetX1NDC(0.5)
stat1->SetY1NDC(0.5)
// in NDC coordinates
// +--------------------+(1,1)
// |             (X2,Y2)|
// |        +---------+ |
// |        |         | |
// |        +---------+ |
// |    (X1,Y1)         |
// |                    |
// |(0,0)               |
// +--------------------+
pad1->cd()
stat1->Draw()

TPaveStats *stat2=(TPaveStats*)pad2->GetPrimitive("stats")
stat2->SetX1NDC(0.5)
stat2->SetY1NDC(0.5)
pad2->cd()
stat2->Draw()

TFile

How to iterative action over items in a directory

1. TFile* f = new TFile("filename")
2. f->cd("dir")
3. gDirectory->pwd()
• ->ls()
• ->GetNkeys(): obtain # of keys in the current dir
• ->GetListOfKeys()
• (TList*)list = gDirectory->GetListOfKey()
4. list->GetSize() : return number of items
• ->At( Int_t 0..GetSize()-1 )
• TObject* After(TObject*)

TFile *tf = new TFile("output.root", "recreate");
...
hp = new TH1F("hp", "Mjj", 50, 0.0, 300.0);
...
tf->Write();
tf->Close();

TString

• TString* str = new TString()
• TString* str = new TString("Test")
• str->Data()
• (const char* 0xb4c3a0c)"Test"
  

TString v
v="Take"
v=="Take"
(unsigned char)1

• str->Append("XXX")
• *str+"DDDD"
  

TString str=TString("hoge")+"foo"
str[1]
(char 111)'o'
str.Length()
(const Int_t)7

Remove

TString v=TString("0123456")
v.Remove(1,1)
v.Data()
    (const char* 0xb4c3844)"023456"

TString v=TString("0123456")
TString s=v(1,2)
s.Data()
    (const char* 0xb86ee54)"12

TPostScript

• TPostScript* ps =new TPostScript("map.ps", 111);

TCanvas* c1=new TCanvas( "c1", "HOGE", 700, 500);
TPostScript* ps =new TPostScript("map.ps", 112);
...
c1->Update();
ps->Clear();
...
ps->Close();

Easy way to plot function

• (new TF1("fun1","(1-x)*sqrt(1-x*x)",-1,1))->Draw();
• (new TF1("fun1","1/sqrt(2*TMath::Pi())*exp(-x*x/2)",-3,3))->Draw();
• (new TF2("fun2","(175/80)**2*(1-y)*(1-x**2)+(1+y)*(1-x)**2",-1,1,-1,1))->Draw("lego")

TF1* f=new TF1("fun1","[0]*(2-[1]+[1]*x*x)/(2-[1]+[1]/3)",0,1);
f->SetParameters(val0,val1);
.. or ..
f->SetParameter(0, val0);
f->SetParameter(1, val1);
...
f->Draw();  DrawCopy("same");

Combination of pre-implemented functions

TF1 * f=new TF1("myfunc", "expo*pol1(2)", 0, 1);
f->SetParameters(1,2,3,4);
f->Draw();
pol1(2) means that the index of pol1 starts from [2], since expo has two parameters [0] and [1]. This is equivalent to
TF1 * f2=new TF1("myfunc", "exp(1+2*x)*(3+4*x)", 0, 1);
f2->Draw();

TText, etc

TText* txt=new TText(0.5, 0.5, "hoge");
txt->SetNDC(kTRUE); // <- use NDC coordinate
txt->SetTextSize(0.04);
txt->Draw();

TLatex* tlx=new TLatex(0.5, 0.5, "#[]{#frac{x^{2}_{i}}{#sqrt{#hat{y}}}}");
tlx->SetNDC(kTRUE); // <- use NDC coordinate
tlx->SetTextSize(0.04);
tlx->Draw();

TLine* l=new TLine(xpos, 0.0 , xpos, hp->GetMaximum());
l->Draw();

TMath

TGraph

// XY Graph  // float xp[n], yp[n]
c1 = new TCanvas("c1", "foo",200,10,600,400);
c1->SetGrid();

TH2F *hr = new TH2F("hr", "hoge", 2, XMIN-XMARGIN, XMAX+XMARGIN, 2, YMIN-YMARGIN, YMAX+YMARGIN);
hr->SetStats(kFALSE);
hr->Draw();

TGraph* g = new TGraph(n, xp, yp);
g->SetMarkerColor(kBlue);
g->SetMarkerStyle(2);
g->Draw("P");

Histograme as a function of time

Cosmetics