ROOT

ROOT

How to use it as an *interactive tool or a script

May also have *bugs to be solved.

Interactive Commands for ROOT

Browse the root file

Use a TBrowser

root [0] gSystem->Load("TTreeViewer");
root [1] TFile file("<file_name>.root");
root [2] new TTreeViewer("<tree_name>");

Or can do this: TBrowser b("<file_name.root>");

the class of an object is the text before the first underline, “_” . In general, the object can be grabbed via *<gallery::Event>.getValidHandle() function.

open a root file:

root -l <name>.root

show classes in the root file:

.ls

Show detail variables of an object (the $n$th object in an example):

vertex_tree->Show(n)

Show brief summary:

vertex_tree->Scan()

Save this summary to a file:

((TTreePlayer*)(T->GetPlayer()))->SetScanRedirect(true);
((TTreePlayer*)(T->GetPlayer()))->SetScanFileName("toto.txt");
   	tree->Scan(...);  

Show number of Entries:

vertex_tree->GetEntries()

Plot according to a given variable

vertex_tree->Draw("<object>","<condition 1>&&<condition 2>")

Plot according to a given variable (with customized bins, e.g. 30 bins ranged from 0 to 1)

vertex_tree->Draw("<object>>>hsqrt(30,0,1)","<condition 1>&&<condition 2>")

Plot them in the same canvas:

vertex_tree->Draw("<object>","<condition 1>&&<condition 2>", "same")

Insert a line in to a histogram (???):

?????.Fit("pol n")

Connect a friend tree (add tree in file2.root to the file1.root)T

TFile f1("file1.root"); //open a root file
TTree * Tree_name = (TTree* )f1.Get("<Existant_Tree_name>");//make a new tree (e.g. vertex_tree) in the root file f1
Tree_name->AddFriend("Friend_tree = Tree_name","file2.root")//copy (link) a friend a tree (e.g. lee_unfolding_tree) to the current root file.
TF->Draw("things to draw");

correction

Tree_name->AddFriend("Tree_name = Friend_tree","file2.root")//copy (link) a friend a tree (e.g. lee_unfolding_tree) to the current root file. --- UI browser

Tbrowser b

---

Draw 2D Histogram (y-axis:x-axisTl)

vertex_tree->Draw("(reco_shower_helper_energy+reco_track_energy_new_legacy):(nu_energy)>>h(100,0,1.5,100,0,1.5)","abs(true_nuvertz-true_track_startz)<1","COLZ")

---

Weight a event, multiple it by some number:

vertex_tree->Draw("nu_energy","lee_unfolding_tree.signal_weight","hist")

---

Set axis of a plot

h->GetXaxis()->SetTitle("name of the x-axis")

Update the canvas

c1->Update()

###Drawing Binning (20 bins, from 0 to 0.7):

vertex_tree->Draw("nu_energy>>Vertice(20,0,0.7)","signal_weight","hist")

Set title:

Vertice->SetTitle("Unfolded Intrinsic #nu_{e}(#bar{#nu}_{e}) Flux Low Energy Excess")
Vertice->GetXaxis()->SetTitle("MC True (Anti-)Electron Neutrino Energy")
Vertice->GetYaxis()->SetTitle("Number of vertices")
c1->Update()

Draw with special variables

Special function

Sum$(variable) will get the sum of each elements in that variable;

###Summary of result via TMVAGui Run a root file:

TMVA::TMVAGui("cosmic_template_training.root")

Make a TTree Class

<TTree_name>->MakeClass("output_file_name")

Delete a TDirecory

Go to update, mode, delete TDirectoryFile contain name MCUnisim, which has two cycle (contains objects inside, no subdirectory inside).

TFile f("hist_elEnuQE_bgap25_s1_h8261672200918285872.root ","update")
f.Delete("*MCUnisims*;2")
f.Write()

Disable warnings

gSystem->RedirectOutput("/dev/null");
 gSystem->RedirectOutput(0,0);//re-activate the pirnt out.

Math

TDecompLU

TDecompLU lu(A) decomposes a matrix A into \(PA=LU\), where $P$ is a permutation matrix, $L$ is unit lower triangular, $U$ is upper triangular. That is, $A$ is analyzed, and $P$, $L$, $U$ are available for further use.

lu.Decompose()

TMatrix

Get dimensions <TMatrix>->GetNrows()

Get contents, (1,1) for example, (*<TMatrix>)(1,1)

Script Snip

Make a canvas for multiple plots (e.g. a 2 columns by 2 rows canvas): TCanvas * c = new TCanvas(); c->Divide(2,2); c->cd(1);# then change to one of the canvas; Make a gif: TPad p = (TPad*)can3d->cd(); can3D->SaveAs("pgif.gif"); for(double k=0; k<= 360.01; k+=1.0){ p->GetView()->RotateView(360-k,k); can3D->Update(); can3D->SaveAs("pgif.gif+3"); } can3D->SaveAs("pgif.gif++");

Bugs and Solutions

Drawing issue

T->Draw("var1","var2")

Warning in <TCanvas::ResizePad>: Inf/NaN propagated to the pad. Check drawn objects.

This could be caused by the Float_t numbers in var2 with infinite digits, and it can be “fixed” by limiting the digits of var2 (change it into int and change it back to Float_t).