RootNotes < Main

Main Web>TWikiUsers>DavidCockerill>RootNotes (2021-10-17, DavidCockerill) (raw view)
---+ Root Notes
<br>
For good/high resolution png plots, MAKE SURE CANVAS HAS ENOUGH PIXELS !!!!!! <br>
ie:  TCanvas *c1 = new TCanvas("c1", "SIC data", 800, 600); <br>
<br>
| [[https://root-forum.cern.ch/index.php][RootTalk]] | [[https://twiki.cern.ch/twiki/bin/view/Main/DavecRoofit][DavecRoofit]] | 

%TOC%

| [[https://root.cern.ch/root/htmldoc/guides/users-guide/ROOTUsersGuide.html][ROOT users guide]] | [[http://root.cern.ch/drupal/][Root homepage]] | [[https://root.cern.ch/root/htmldoc/guides/primer/ROOTPrimer.html][ROOT primer]] | [[https://root.cern.ch/faq-page#faq-expand-all-link][FAQs]] <!-- END --> |
| [[http://root.cern.ch/root/html/ClassIndex.html][ROOT Class Index]] | [[http://root.cern.ch/root/html/TH1.html#TH1:GetBinContent%1][Histograms, TH1, TH2D methods etc]] | [[https://root.cern.ch/doc/master/classTF1.html][TF1 methods]] | [[http://root.cern.ch/root/html/TH1.html][Fit with TF1 etc]] <!-- END --> |
| [[http://home.fnal.gov/~apana/roottips.html][Useful ROOT tips !!!]] | [[https://root.cern.ch/phpBB3/viewtopic.php?t=15821][Multi histos - looping/filling]] | [[http://physics.bu.edu/neppsr/2007/TALKS-2007/ROOT_Tutorial_Bose.pdf][Tulika - ROOT tutorial]] | [[http://ihp-lx.ethz.ch/CompMethPP/root/Introduction_to_ROOT.pdf][Luca Perrozzi - ROOT tutorial]] <!-- END --> |

| [[http://www-root.fnal.gov/root/GettingStarted/GS.htm][fnal root tips]] | [[https://root.cern.ch/root/html/tutorials/hist/ratioplot.C.html][Pad tricks for axes]] |

<img src="%ATTACHURLPATH%/pict1_TColor_002.png" alt="pict1_TColor_002.png" width="396" height="372" />
<br>

*Command line options*
<verbatim>
These are some command line options you can use when starting ROOT:
-b: ROOT session runs in batch mode, without graphics display. This mode is useful in case you do not want to set the DISPLAY.
-n: Does not execute the logon script and logoff script as specified in .rootrc.
-q: Exits after processing the command line macro files.
-l: Does not show the ROOT banner.
-a: Displays the ROOT splash screen.
-x: Exits on exception.
dir: If dir is a valid directory, change to it (cd) before executing ROOT.
-?, -h, --help: Prints usage.
</verbatim>

*ROOTSYS and PATH AT CERN,  30 MARCH 2021*
<verbatim>
~/<1>src/Reco/RecoAnalyzer $ echo $ROOTSYS
/cvmfs/cms.cern.ch/slc6_amd64_gcc530/lcg/root/6.06.00-ikhhed4/

echo $PATH
/cvmfs/cms.cern.ch/share/overrides/bin:
/afs/cern.ch/user/d/davec/CMSSW_8_0_19_patch1/bin/slc6_amd64_gcc530:
/afs/cern.ch/user/d/davec/CMSSW_8_0_19_patch1/external/slc6_amd64_gcc530/bin:
/cvmfs/cms.cern.ch/slc6_amd64_gcc530/cms/cmssw-patch/CMSSW_8_0_19_patch1/bin/slc6_amd64_gcc530:
/cvmfs/cms.cern.ch/slc6_amd64_gcc530/cms/cmssw-patch/CMSSW_8_0_19_patch1/external/slc6_amd64_gcc530/bin:
/cvmfs/cms.cern.ch/slc6_amd64_gcc530/cms/cmssw/CMSSW_8_0_19/bin/slc6_amd64_gcc530:
/cvmfs/cms.cern.ch/slc6_amd64_gcc530/external/llvm/3.7.1-giojec/bin:
/cvmfs/cms.cern.ch/slc6_amd64_gcc530/external/gcc/5.3.0/bin:
/cvmfs/cms.cern.ch/slc6_amd64_gcc530/lcg/root/6.06.00-ikhhed4/bin:
/afs/cern.ch/cms/caf/scripts:
/cvmfs/cms.cern.ch/common:
/usr/sue/bin:/usr/lib64/qt-3.3/bin:
/usr/local/bin:
/usr/bin:
/usr/local/sbin:
/usr/sbin:
/opt/puppetlabs/bin:
/afs/cern.ch/project/eos/installation/pro/bin/:
/afs/cern.ch/sw/lcg/app/releases/ROOT/6.02.00/x86_64-slc6-gcc48-opt/root//bin:
/afs/cern.ch/user/d/davec/MyCode/
</verbatim>

*ROOTSYS and PATH on my MAC,  30 MARCH 2021*
<verbatim>
HEPMBP069:~ david$ echo $ROOTSYS
/Users/david/Downloads/root

HEPMBP069:~ david$ echo $PATH
/Users/david/Downloads/root/bin:
/usr/bin:
/bin:
/usr/sbin:
/sbin:
/usr/local/bin:
/opt/X11/bin
</verbatim>



*On Ubuntu, 30 March 2021* <br>
https://root-forum.cern.ch/t/root-installation-issues-on-ubuntu-18-04/33047
<verbatim>
you don’t have to compile ROOT from source on Ubuntu.

You can download pre-compiled binaries (https://root.cern/downloading-root)
that you just need to uncompress, 

and a source /path/to/ROOT/bin/thisroot.sh) gives you a working ROOT.
</verbatim>

*Batch mode* <br>
gROOT->SetBatch(1); <br>
Back to Grapnics mode: <br>
gROOT->SetBatch(0); 

*Turn off stats* <br>
gStyle->SetOptStat(0); <br>

*TLegend* <br>
TLegend(Double_t x1,Double_t y1,Double_t x2,Double_t y2,const char *header,         Option_t *option) <br>
The  legend  is  defined  with  default  coordinates,  border  size  and  option.  The  legend  coordinates  (NDC)  in  the  current pad are x1, y1, x2, y2. The default text attributes for the legend are: 
   * Alignment    = 12 left adjusted and vertically centered  
   * Angle  = 0 (degrees)  
   * Color = 1 (black) 
   * Size  = calculate when number of entries is known 
   * Font  = helvetica-medium-r-normal scalable font = 42, and bold = 62 for title
gStyle->SetLegendBorderSize(0); for no bounding box <br>
legendbtcp->SetTextSize(0.03);  
   * Dont use mumbers > 1.0. This only works if the font is a pixel-based one; else try 0.03 or similar values.<br>
<br>
AddEntry(TObject *obj, const char *label,Option_t *option) <br>
The parameters are: <br>
   * obj is a pointer to an object having marker, line, or fill attributes (a histogram, or a graph) 
   * label is the label to be associated to the object 
   * option:  
   * ”L” draw line associated with line attributes of obj, if obj inherits from TAttLine. 
   * ”P” draw poly-marker associated with marker attributes of obj, if obj inherits TAttMarker. 
   * ”F” draw a box with fill associated with fill attributes of obj, if obj inherits TAttFill

*Plot single point* <br>
<verbatim>
TMarker m(.5,.5,22);  // x,y, marker type !!!!!!!!
m.Draw();

or
TMarker tt; 
tt.SetMarkerStyle(20);
tt.SetMarkerSize(0.8);
tt.DrawMarker(.5,.5);

or, for a point in a 3D plot:
{
  TGraph2D* t = new TGraph2D(1);
  t->SetPoint(0, 1. , 2. , 3.);
  
  t->GetXaxis()->SetLimits(0, 2);
  t->GetYaxis()->SetLimits(1, 3);
  t->GetZaxis()->SetLimits(2, 4);
  
  //  t->GetXaxis()->SetRangeUser(0, 2);
  //  t->GetYaxis()->SetRangeUser(1, 3);
  t->GetZaxis()->SetRangeUser(2, 4);
  
  t->Draw("P0");
}
</verbatim>

*Change title* <br>
<verbatim>
gStyle->SetOptTitle(0); 
TPaveLabel *title = new TPaveLabel(.11,.95,.35,.99,"my new title","brndc"); 
title->Draw();
</verbatim>

<br>
[[https://root.cern.ch/canvases-and-pads][Canvases and pads]] 
<br>
<br>

*TLatex in NDC coordinates* <br>
NDC coordinates: canvas or pad ranges from 0 to 1, in both x and y.
<verbatim>
TLatex tt; 
tt.DrawLatexNDC(0.01,0.01,"mytext");
</verbatim>

*Convert string to const char * for TFile name*
<verbatim>
std::string str;
const char * c = str.c_str();

  //std::string str;
  const char * c = s.c_str();
  //s = "Run-" + s + ".root";
  TFile f(c, "RECREATE");
</verbatim>

*Put run number into histo title*
<verbatim>
  string s, s1, s2;
  TString tsrun;

  s1 = to_string(328337);
  s2 = to_string(328338);

  s = "Runs " + s1 + " and " +s2;

  cout<< "\n\nString is " << s <<endl;
  tsrun = s;
  cout << tsrun << endl;

TH2D *EEPlaser1pnratio = new TH2D("EEPlaser1pnratio", tsrun + ", EEP, pn ratio, pn g=16/pn g=1, laser power = 1", 100, 0, 100, 100, 0, 100);
</verbatim>

*TGraph constructors - only these are valid !!!* <br>
<verbatim>
 	TGraph (Int_t n, const Int_t *x, const Int_t *y)
 	Graph normal constructor with ints. More...
 
 	TGraph (Int_t n, const Float_t *x, const Float_t *y)
 	Graph normal constructor with floats. More...
 
 	TGraph (Int_t n, const Double_t *x, const Double_t *y)
 	Graph normal constructor with doubles. More...
</verbatim>

*TGraph options* <br>
[[https://root.cern.ch/doc/master/classTGraphPainter.html][Painter options]] <br>
Graphs' plotting options
<verbatim>
Graphs can be drawn with the following options:
Option 	Description
"A" 	Axis are drawn around the graph
"I" 	Combine with option 'A' it draws invisible axis
"L" 	A simple polyline is drawn
"F" 	A fill area is drawn ('CF' draw a smoothed fill area)
"C" 	A smooth Curve is drawn
"*" 	A Star is plotted at each point
"P" 	The current marker is plotted at each point
"B" 	A Bar chart is drawn
"1" 	When a graph is drawn as a bar chart, this option makes the bars start from the bottom of the pad. By default they start at 0.
"X+" 	The X-axis is drawn on the top side of the plot.
"Y+" 	The Y-axis is drawn on the right side of the plot.
"PFC" 	Palette Fill Color: graph's fill color is taken in the current palette.
"PLC" 	Palette Line Color: graph's line color is taken in the current palette.
"PMC" 	Palette Marker Color: graph's marker color is taken in the current palette.
"RX" 	Reverse the X axis.
"RY" 	Reverse the Y axis. 
</verbatim>
<br>

*Directories* <br>
[[https://root-forum.cern.ch/t/getting-histograms-from-a-tdirectoryfile/27532][histos from a directory]] <br>
[[http://ihp-lx.ethz.ch/CompMethPP/root/Introduction_to_ROOT.pdf][Intro]] <br>



*Get data from a Canvas saved as a root file* <br>
[[https://root-forum.cern.ch/t/error-fitting-histo-from-a-canvas/15097/2][From a canvas or a pad]] <br>
<verbatim>
TFile miofile(“test.root”);
TCanvas can = (TCanvas)miofile.Get(“c1”);
TH1D his = ((TH1D)(can->FindObject(“MCA”)));
Double_t xmin = his->GetBinCenter(1);
Double_t xmax = his->GetBinCenter(his->GetNbinsX());
his->Fit(“gaus”, “”, “”, xmin, xmax);
can->Draw();

TFile miofile(“test.root”);
TCanvas can = (TCanvas)miofile.Get(“c1”);
((TPad *)can->FindObject(“pad1”))->GetListOfPrimitives()->ls();
((TPad *)can->FindObject(“pad1”))->GetListOfPrimitives()->Print();
TH1D his = ((TH1D)(((TPad *)can->FindObject(“pad1”))->GetPrimitive(“MCA”)));
Double_t xmin = his->GetBinCenter(1);
Double_t xmax = his->GetBinCenter(his->GetNbinsX());
his->Fit(“gaus”, “”, “”, xmin, xmax);
can->Draw();
Mr.M
Oct '12

Thank you very very much!
can->FindObject(“MCA”) was the trick. :smiley:

</verbatim>
<br>
[[https://root.cern.ch/root/roottalk/roottalk04/2632.html][Rene answer]] <br>
<br>
<verbatim>
I wrote a canvas in a file and now I'd like to
get back the histogram from the 
canvas and do some stuff...
This is the 1st script:

   TFile miofile("Hfra40.root","read");
   miofile->ls();
   TCanvas *c1 = (TCanvas*)miofile.Get("c1");
   c1->Draw();

the c1 canvas is drawn and this is the output:
TFile**         Hfra40.root
 TFile*         Hfra40.root
  KEY: TCanvas  c1;1    c1
</verbatim>
<br>
<verbatim>
Attilio,
   In your 2nd script, do;
{    
   TFile miofile("Hfra40.root","read");
   TH1F *hFra40;
   TCanvas *c1 = (TCanvas*)miofile.Get("c1");
   hFra40 = (TH1F*)c1->GetPrimitive("hFracEtcorr2Part");
    c1->Clear();
    c1->Draw();
   hFra40->Draw();
}
or
{
   TFile miofile("Hfra40.root","read");
   TH1F *hFra40;
   TCanvas *c1 = (TCanvas*)miofile.Get("c1");
   hFra40 = (TH1F*)c1->GetPrimitive("hFracEtcorr2Part");
   TCanvas c2;
   hFra40->Draw();
}
In your original script, the current pad/canvas is c1.
So you draw the histogram in this canvas.
   Rene Brun  
</verbatim>

<br>
<br>
*TDatime*
[[http://root.cern.ch/root/html/TDatime.html][Info]] <br>
<verbatim>
TDatime t;
t.Set(....);
</verbatim>


*Plot single point* <br>
TMarker m(.5,.5,22); <br>
m.Draw(); <br>

*TFiles - directories and input/output* <br>
Chap 11: Input/Output <br>

*How to show pdf, ps, eps in canvas* <br>
[[https://root.cern.ch/root/html/tutorials/graphics/psview.C.html][tutorial]] <br>


*Greek symbols* <br>
#eta etc <br>
<br>

*Getting info from TGraphs* <br>
[[https://root-forum.cern.ch/t/integral-of-tgraph/4745/8][Manipulations !!!]]

<verbatim>
//search points (may be more than 1)
Int_t j = 0;
for (j=0;j<n;j++) {
if (TMath::AreEqualRel(0.5,gr->GetX()[j],1e-6)) {
printf(“found point %d with x=%g, y=%g\n”,j,gr->GetX()[j],gr->GetY()[j]);
}
</verbatim>

*Writing/reading TGraphs* <br>
Only histograms and trees are written when calling TFile::Write(). All other objects like TGraphs have to be each written out explicitly.
[[https://root.cern.ch/root/roottalk/roottalk01/3310.html][Rene Brun answer]] <br>
<verbatim>
Float_t x[5] = {1, 2, 3, 4, 5};
Float_t y[5] = {3, 3, 3, 3 ,3};
Float_t ex[5] = {1, 1, 1, 1, 1};
Float_t ey[5] = {1, 1, 1, 1 ,1};
 
TFile f("test.root",  "RECREATE");
TGraph *g = new TGraphErrors(5, x, y, ex, ey);
//g->Draw("AP");
g->SetName("hello");
g->Write();
f.Close();
delete f;
</verbatim>
<br>
<verbatim>
As suggested above, you can write your graphs one by one to the file
or alternatively add the graphs to the list of objects associated
to the file with
f->GetList()->Add(gr1);
f->GetList()->Add(gr2); //etc
f->Write(); //will write all the objects in the list
In this case, you better give a name to your graphs

When you want to draw the graph in a file
-via TBrowser, double click on the graph. If you use a version >= 4.02
the graph will be drawn by default with option “alp”.
you can change this default option by setting
TGraph::BrowseOption: alp
in the file .rootrc or $ROOTSYS/etc/system.rootrc

-via the command
TGraph gr1 = (TGraph)f->Get(“name of gr1”);
gr1->Draw(“alp”); //or any other option
</verbatim>
<br>
<verbatim>
Only TH1 and TTree objects are automatically registered to
gDirectory->GetList(). TGraphs are not.

You can register any TObject derived object (eg TGraph) to this list with a
statement like
  gDirectory->Append(mygraph);
where TGraph *mygraph is an already existing TGraph.

You can replace your saveAll function with
   gDirectory->Write();
This statement will write all objects registered in the directory.

To see the list of objects in a directory, do
  dir->ls(), eg gDirectory->ls();

Rene Brun
</verbatim>


*Getting global variables from another file* <br>
Just list all the variables in the other file, no {} needed at start/end of file, and do: <br>
<verbatim>
#include "sic-btcp-lcf-info.C"
void Drawlcps() {
...........can now use the variables listed in sic-btcp-lcf-info.C, they are now global variables
}

and in root:
> .L corr-fac-vs-int-lumi-300-with-extraps.C   // the file which has the function:  void Drawlcps() {...}
> Drawlcps()
</verbatim>

<br>
*Colour, Markers and styles* <br>
[[https://root.cern/doc/v610/pict1_TColor_002.png][Colour wheel]] at [[https://root.cern/doc/v610/classTColor.html][link]] <br>
[[https://root.cern.ch/doc/master/pict1_TAttText_003.png][Text colour map]] at [[https://root.cern/doc/v610/classTAttText.html][link]] <br>
[[https://root.cern/doc/v610/pict1_TAttMarker_002.png][Marker styles]] at [[https://root.cern/doc/v610/classTAttMarker.html][link]] <br>
[[https://root.cern.ch/root/htmldoc/guides/users-guide/pictures/030000D2.png][Fill styles]] at [[https://root.cern.ch/root/htmldoc/guides/users-guide/ROOTUsersGuide.html#setting-the-style][link]] and [[https://root.cern.ch/root/htmldoc/guides/users-guide/ROOTUsersGuide.html#fill-attributes][link2]]

| [[https://root-forum.cern.ch/t/setting-histogram-title-size-in-root/4468][Text discussion]] | [[http://www.usatlas.bnl.gov/~dladams/muon/plots/dijet_tutorial/macros/rootlogon.C][atlas logon]] |

Examples: <br>
myObject.SetFillColor(kRed); <br>
myObject.SetFillColor(kYellow-10); <br>
myLine.SetLineColor(kMagenta+2); <br>


| gROOT->ProcessLine(".! echo $ROOTSYS"); | ProcessLine to execute other code from within one program |
| gROOT->Reset() | When running an un-named script over again, and this is frequently the case<br> since un-named scripts are used to prototype, one should reset <br>the global environment to clear the variables with gROOT->Reset() |

| TString | [[https://root.cern.ch/root/html303/examples/tstring.C.html][Examples, use of the TString class]] | 
| TGraph | [[https://root.cern.ch/doc/master/classTGraph.html][TGraph methods]] |


*%RED%Fast tip%ENDCOLOR%*: <br>
2D plot, with Browser editor, click inside the plot and in editor check boxes "col" and "palette" to see the z-value palette bar on the RHS.<br> Also h2->Draw("zcol"); 


*Canvas/Histo setups* <br>
[[https://root.cern.ch/root/roottalk/roottalk06/1525.html][SetTitle question]] <br>
Please read the documentation of TStyle::SetTitleFont <br>
[[http://root.cern.ch/root/htmldoc/TStyle.html#TStyle:SetTitleFont][TStyle:SetTitleFont]]
<verbatim>
> =====
> void SetTitleFont(Style_t font, Option_t *axis)
> if axis =="x" set the X axis title font
> if axis =="y" set the Y axis title font
> if axis =="z" set the Z axis title font
> any other value of axis will set the pad title font
> if axis="xyz" set all 3 axes
> ====
>
> gStyle->SetTitleFont(62);
> gStyle->SetTitleFontSize(0.09);
</verbatim>
Also note that if you select a font style in pixels (63), ie: gStyle->SetTitleFont(63,""); <br>
you should specify a *number of pixels* for the font size. See class description at [[http://root.cern.ch/root/htmldoc/TAttText.html][TAttText]].

*Text Font and Precision* <br>
The text font code is combination of the font number and the precision.  <br>
Text font code = 10*fontnumber + precision  <br>
Font numbers must be between 1 and 14.  <br>
The precision can be:
<verbatim>
precision = 0 fast hardware fonts (steps in the size)
precision = 1 scalable and rotatable hardware fonts (see below)
precision = 2 scalable and rotatable hardware fonts
precision = 3 scalable and rotatable hardware fonts. Text size is given in pixels.

List of the currently supported fonts:
Font number         X11 Names             Win32/TTF Names
    1 :       times-medium-i-normal      "Times New Roman"
    2 :       times-bold-r-normal        "Times New Roman"
    3 :       times-bold-i-normal        "Times New Roman"
    4 :       helvetica-medium-r-normal  "Arial"
    5 :       helvetica-medium-o-normal  "Arial"
    6 :       helvetica-bold-r-normal    "Arial"
    7 :       helvetica-bold-o-normal    "Arial"
    8 :       courier-medium-r-normal    "Courier New"
    9 :       courier-medium-o-normal    "Courier New"
   10 :       courier-bold-r-normal      "Courier New"
   11 :       courier-bold-o-normal      "Courier New"
   12 :       symbol-medium-r-normal     "Symbol"
   13 :       times-medium-r-normal      "Times New Roman"
   14 :                                  "Wingdings"
   15 :       Symbol italic (derived from Symbol)
</verbatim>
[[https://root.cern.ch/doc/master/pict1_TAttText_004.png][Font images]].

*Font quality and speed* <br>
When precision 0 is used, only the original non-scaled system fonts are used. <br>
The fonts have a minimum (4) and maximum (37) size in pixels. <br>
These fonts are fast and are of good quality. Their size varies with large steps and they cannot be rotated. 

Precision 1 and 2 fonts have a different behaviour depending if the True Type Fonts (TTF) are used or not. <br>
If TTF are used, you always get very good quality scalable and rotatable fonts. However TTF are slow.

How to use True Type Fonts <br>
One can activate the TTF by adding (or activating) the following line in the .rootrc file:
<verbatim>
Unix.*.Root.UseTTFonts:     true
It is possible to check the TTF are in use in a Root session with the command:
gEnv->Print();

If the TTF are in use, the following line will appear at the beginning of the printout given by this command:
Unix.*.Root.UseTTFonts:   true                           [Global]
</verbatim>

*TStyle Class Reference* [[https://root.cern.ch/doc/master/classTStyle.html#a6bcb65069ebf4d4153bd3e2def0e8d64][link]] <br>
TStyle default settings at [[https://root.cern.ch/doc/master/core_2base_2src_2TStyle_8cxx_source.html][link]] <br>
This class includes functions to set some of the following object attributes:
<verbatim>
Canvas
Pad
Histogram axis
Lines
Fill areas
Text
Markers
Functions
Histogram Statistics and Titles
</verbatim>
Set font number for axis labels. SetLabelFont(): void TStyle::SetLabelFont	(	Style_t 	font = 62, Option_t * 	axis = "X" ) <br>	
Set size of axis labels.  SetLabelSize():   void TStyle::SetLabelSize	(	Float_t 	size = 0.04,  Option_t * 	axis = "X"  )	<br>	
The size is expressed as a percent of the pad height, unless precision = 3. axis specifies which axis ("x","y","z"), default = "x" if axis="xyz" set all 3 axes <br>
Definition at line 1072 of file [[https://root.cern.ch/doc/master/core_2base_2src_2TStyle_8cxx_source.html][TStyle.cxx]].

*Text Size* <br>
If the text precision (see next paragraph) is smaller than 3, the text size (textsize) is a fraction of the current pad size. Therefore the same textsize value can generate text outputs with different absolute sizes in two different pads. The text size in pixels (charheight) is computed the following way:
<verbatim>
pad_width  = gPad->XtoPixel(gPad->GetX2());
pad_height = gPad->YtoPixel(gPad->GetY1());
if (pad_width < pad_height)  charheight = textsize*pad_width;
else                         charheight = textsize*pad_height;
</verbatim>
If the text precision is equal to 3, the text size doesn't depend on the pad's dimensions. A given textsize value always generates the same absolute size. The text size (charheight) is given in pixels:  charheight = textsize; <br>
Note that to scale fonts to the same size as the old True Type package a scale factor of 0.93376068 is apply to the text size before drawing.

The text size of any class inheriting from TAttText can be changed using the method SetTextSize and retrieved using the method GetTextSize.

*Histogramme draw options* <br>
[[https://root.cern.ch/root/htmldoc/guides/users-guide/ROOTUsersGuide.html#draw-options][options]] <br>
[[https://root-forum.cern.ch/t/how-to-draw-pad-with-residuals-below-an-histogram/6820][Residuals below a histogram]] <br>

*Draw histogram without the vertical lines for the first and the last bin* <br>
Use “][” 

*Good resolution pngs for ppt* <br>
Expand canvas to as large a size as possible before saving as png <br>

*Quick histo reminder*
<verbatim>
#include <TH2.h>

TH1F *iprod1 = new TH1F("iprod1","iprod distn",12,-2,10);
TH2D *iprod2 = new TH2D("iprod2","EE- types",100,0,100,100,0,100);
TH2D *iprod3 = new TH2D("iprod3","EE+ types",100,0,100,100,0,100);
</verbatim>

*Getting the bin content at x,y:*
<verbatim>
(TH1::GetBinContent(TH1::FindBin(x,y))
ie
hEE->GetBinContent(  hEE->FindBin(x,y)  )
</verbatim>

Get the bin centers for a point (x,y):
<verbatim>
x_=h2D->GetXaxis()->GetBinCenter( h2D->GetXaxis()->FindBin(x) );
y_=h2D->GetYaxis()->GetBinCenter( h2D->GetYaxis()->FindBin(y) );
</verbatim>

*Using more than one TFile:*
<verbatim>
cout << "Histos available on disk, before TFiles: " << endl;
  gDirectory->ls("-d");
   cout << "Histos available in memory, before TFiles: " << endl;
  gDirectory->ls("-m");
  cout << "\n\n" << endl;  

  TFile f ("histo-reco.root");
  //f.cd("demo");  
  //h002->Draw();

 cout << "Histos available on disk, after TFile f (histo-reco.root) : " << endl;
  gDirectory->ls("-d");
   cout << "Histos available in memory, after TFile f (histo-reco.root) : " << endl;
  gDirectory->ls("-m");
  cout << "\n\n" << endl;  

  TFile ff ("result-of-adding.root");

  TFile fff ("EBdata.root");

.........
 f.cd("demo");
TH1 *EEMcs2 = (TH1*)EEMcs->Clone("EEMcs2"); // EE- status
........
 ff.cd("");
  TH1 *iprod22 = (TH1*)iprod2->Clone("iprod22");

 fff.cd("");
 TH1 *EBiprod2 = (TH1*)EBiprod->Clone("EBiprod2"); // btcp = 1, SIC = 2, preprod = 3
 TH1 *EBiproddist2 = (TH1*)EBiproddist->Clone("EBiproddist2"); // btcp = 1, SIC = 2, preprod = 3
..........
</verbatim>

*Plotting multiple graphs* <br>
https://root-forum.cern.ch/t/draw-multiple-graphs/5418 <br>
https://root.cern.ch/doc/master/classTMultiGraph.html:
<verbatim>
   TGraph *g[10];
   Double_t x[10] = {0,1,2,3,4,5,6,7,8,9};
   Double_t y[10] = {1,2,3,4,5,6,4,3,2,1};
   TMultiGraph *mg = new TMultiGraph();
   for (int i=0; i<10; i++) {
      g[i] = new TGraph(10, x, y);
      y[i] = y[i]+1;
      mg->Add(g[i]);
   }

   mg->Draw("AL");
// will auto draw x-y ranges to fit all graphs

// changing mg ranges
// need GetXaxis for x-axis range <-- with decimal not integer numbers !!!!!!!
// need SetMinimum and SetMaximum for y-axis range <-- with decimal not integer numbers !!!!!!!
mg3040->GetXaxis()->SetLimits(690., 720.)
root [4] mg3040->SetMinimum(-1.5)
root [5] mg3040->SetMaximum(1.1)
 </verbatim>



*Saving histos to a file:*
<verbatim>
save the histograms to a file
root[14] TFile* file = new TFile("exercise0.root","RECREATE")
and now we can write the histograms and close the file
root[15] myhisto.Write()
root[16] histo->Write()
root[17] file->Close()
root[18] delete file
Now try to read the histograms back in:
root[19] TFile* fileagain = new TFile("exercise0.root","READ")
root[20] TH1F * histoagain = (TH1F*)fileagain->Get("histo");
</verbatim>

*Histo methods* <br>
[[https://root.cern.ch/doc/master/classTH1.html#adb2021fb94eab12f64a8e32e69457cac][link]] : <br>
Clone a histogramme from another, ie h from h1:
<verbatim>
TH1F *h = (TH1F*)h1->Clone("h");

virtual Bool_t 	Add (const TH1 *h1, Double_t c1=1)
 Performs the operation: this = this + c1*h1 If errors are defined (see TH1::Sumw2), errors are also recalculated. More...

virtual Bool_t 	Add (const TH1 *h, const TH1 *h2, Double_t c1=1, Double_t c2=1)
Replace contents of this histogram by the addition of h1 and h2. More...

Bool_t TH1::Divide	(	TF1 * 	f1, Double_t 	c1 = 1 )
Performs the operation: this = this/(c1*f1) if errors are defined (see TH1::Sumw2), errors are also recalculated.

Bool_t TH1::Divide	(	const TH1 * 	h1	)	
Divide this histogram by h1.
this = this/h1 if errors are defined (see TH1::Sumw2), errors are also recalculated.


Bool_t TH1::Divide	(	const TH1 * 	h1, const TH1 * 	h2, Double_t 	c1 = 1, Double_t 	c2 = 1, Option_t * 	option = "" )		
Replace contents of this histogram by the division of h1 by h2.
this = c1*h1/(c2*h2)
If errors are defined (see TH1::Sumw2), errors are also recalculated
</verbatim>

Note: //(*EETPmean)=(*EETPrad)/(*EETPradhits);  // operations can be done with histogram pointers <br>
led to problems to do EETPmean->Write(); <br>
Got a 2nd version of  EETPrad, EETPrad;1 and also EETPrad;2 in place of EETPmean. <br>
Instead do:
<verbatim>
TH1F *EETPmean = new TH1F("EETPmean","EE testpulse mean vs radius, sqrt(ix**2 + iy**2); Radius,  sqrt(x*x + y*y)", 60, 0., 60.);
     EETPmean->TH1::Add(EETPrad);
     EETPmean->TH1::Divide(EETPradhits);
     EETPmean->SetTitle("EE testpulse mean vs radius, sqrt(ix**2 + iy**2) " )  ;
     EETPmean->SetXTitle("Radius, sqrt(x*x + y*y)" );
</verbatim>


Int_t TH1::FindBin	(	Double_t 	x, Double_t 	y = 0, Double_t 	z = 0 )	<br>	
Return Global bin number corresponding to x,y,z.

Bool_t TH1::Multiply	(	TF1 * 	f1, Double_t 	c1 = 1 )		<br>	
Performs the operation: this = this*c1*f1 if errors are defined (see TH1::Sumw2), errors are also recalculated.

Bool_t TH1::Multiply	(	const TH1 * 	h1, const TH1 * 	h2, Double_t 	c1 = 1, Double_t 	c2 = 1, Option_t * 	option = "" )		
<verbatim>
Replace contents of this histogram by multiplication of h1 by h2.
this = (c1*h1)*(c2*h2)
If errors of this are available (TH1::Sumw2), errors are recalculated
</verbatim>

Setting the bin content:
<verbatim>
virtual void 	SetBinContent (Int_t bin, Double_t content)
Set bin content see convention for numbering bins in TH1::GetBin 
</verbatim>

gROOT->ls() ; // to get to objects in memory !!!!!!!!!!!<br>

TLIne t <br>
NOTE, assigning TLIne t(2,3,4,5); then t.SetLineColor(2) may not work !!!! 

Better to do just TLIne t. and then use t.DrawLine itself. ) <br>
t.DrawLine(2,3,4,5) // using DrawLine to do repeat dwgs with same object, t <br> 
t.DrawLine(6,7,4,5) <br> 
TLatex tx; <br>
tx.DrawLatex(6.0,7.5," some text")  // using DrawLatex to do repeat dwgs with different text with same object, tx <br> 

Changing frame normalisation:<br>
TLatex latex <br>
latex.DrawLatexNDC(0.1,0.1,"text"); <br>
or <br>
latex.SetNDC(); <br>
latex.DrawLatex(0.1,0.1,"text");


---++ Conventions and Types
Coding Conventions</br>
From the first days of ROOT development, it was decided to use a set of coding conventions. This allows a
consistency throughout the source code. Learning these will help you identify what type of information you are
dealing with and enable you to understand the code better and quicker. Of course, you can use whatever
convention you want but if you are going to submit some code for inclusion into the ROOT sources, you will
need to use these.<br>
These are the coding conventions:<br>
<verbatim>
• Classes begin with T: TLine, TTree
• Non-class types end with _t: Int_t
• Data members begin with f: fTree
• Member functions begin with a capital: Loop()
• Constants begin with k: kInitialSize, kRed
• Global variables begin with g: gEnv
• Static data members begin with fg: fgTokenClient
• Enumeration types begin with E: EColorLevel
• Locals and parameters begin with a lower case: nbytes
• Getters and setters begin with Get and Set: SetLast(), GetFirst()
</verbatim>

Machine Independent Types<br>
Different machines may have different lengths for the same type. The most famous example is the int type. It
may be 16 bits on some old machines and 32 bits on some newer ones. To ensure the size of your variables,
use these pre defined types in ROOT:
<verbatim>
• Char_t Signed Character 1 byte
• UChar_t Unsigned Character 1 byte
• Short_t Signed Short integer 2 bytes
• UShort_t Unsigned Short integer 2 bytes
• Int_t Signed integer 4 bytes
• UInt_t Unsigned integer 4 bytes
• Long64_t Portable signed long integer 8 bytes
• ULong64_t Portable unsigned long integer 8 bytes
• Float_t Float 4 bytes
• Double_t Float 8 bytes
• Double32_t Double 8 bytes in memory, written as a Float 4 bytes
• Bool_t Boolean (0=false, 1=true)
</verbatim>

---++ Root trees/ntuples, read in ascii file

Read in 2 ascii data files. Types defined in .dat files.<br>
Each variable loaded from its corresponding branch object.<br>
| [[%ATTACHURL%/basic-vpts-john-wood-linux-data.dat][Extra .dat file: basic-vpts-john-wood-linux-data.dat]] |

Read in an ascii file with floats, integers and character strings. Types defined in .dat file.<br>
Each variable loaded from its corresponding branch object.<br>
| [[%ATTACHURL%/Tree-vpts-types-in-dat-file.c][Tree-vpts-types-in-dat-file.c]] |  [[%ATTACHURL%/basic-vpts-with-types.dat][basic-vpts-with-types.dat]] |

Read in an ascii file with floats, integers and character strings. Types defined in .C file.<br>
Each variable loaded from its corresponding branch object.<br>
| [[%ATTACHURL%/Tree-test.C][Tree-test.C]] | [[%ATTACHURL%/basic.dat][basic.dat]] |

Tree branch:
<verbatim>
tree->Branch("Ev_Branch",&event,"temp/F:ntrack/I:nseg:nvtex:flag/i ");
The first parameter is the branch name.

The second parameter is the address from which the first variable is to be read. In the code
above, “event” is a structure with one float and three integers and one unsigned integer. 

You should not assume that the compiler aligns the elements of a structure without gaps. To avoid
alignment problems, you need to use structures with same length members. If your structure does not qualify,
you need to create one branch for each element of the structure.

The leaf name is NOT used to pick the variable out of the structure, but is only used as the name for the leaf.
This means that the list of variables needs to be in a structure in the order described in the third parameter.

The third parameter is a string describing the leaf list. Each leaf has a name and a type separated by a "/". 
It is separated from the next leaf by a ":".
</verbatim>

Examples:<br>
Two leafs: a floating-point number called temp and an integer named ntrack.
"temp/F:ntrack/I:"

The type can be omitted and if no type is given, the same type as the previous variable is assumed. <br>
The leaf list below has three integers called ntrack, nseg, and nvtex.<br>
"ntrack/I:nseg:nvtex" 

*When no type is given for the very first leaf, it becomes a float (F).*<br>
The leaf list below has three floats called temp, mass, and px.<br>
"temp:mass:px"

Can add a leaf that holds an entire array of variables. To add an array of floats use the f[n] notation when describing the leaf.<br>
Float_t f[10];<br>
tree->Branch("fBranch",f,"f[10]/F");

You can also add an array of variable length:
<verbatim>
{
TFile *f = new TFile("peter.root","recreate");
Int_t nPhot;
Float_t E[500];
TTree* nEmcPhotons = new TTree("nEmcPhotons","EMC Photons");
nEmcPhotons->Branch("nPhot",&nPhot,"nPhot/I");
nEmcPhotons->Branch("E",E,"E[nPhot]/F");
}
</verbatim>

List of tree variable types:
<verbatim>
The symbols used for the type are:
• C: a character string terminated by the 0 character
• B: an 8 bit signed integer
• b: an 8 bit unsigned integer
• S: a 16 bit signed integer
• s: a 16 bit unsigned integer
• I: a 32 bit signed integer
• i: a 32 bit unsigned integer
• L: a 64 bit signed integer
• l: a 64 bit unsigned integer
• F: a 32 bit floating point
• D: a 64 bit floating point
</verbatim>

---++ Root hints

*Book multiple histogrammes* <br>
<verbatim>
Create a dynamic array of pointers
TH1F** h = new TH1F*[m];
for (int i=0;i<m;i++) {
h[i] = new TH1F(name,title... 

Rene Brun
</verbatim>
see [[https://root.cern.ch/phpBB3/viewtopic.php?t=1309][root faq]]

*Copy a histogramme from one file to another from the command line* <br>
rootcp xtal-types.root:iprod2 result-of-adding.root <br>

*Histogram bins etc* <br>
[[https://root.cern.ch/doc/master/classTH1.html][TH1 methods]] <br>

bin = 0;       underflow bin <br>
bin = 1;       first bin with low-edge xlow INCLUDED <br>
bin = nbins;   last bin with upper-edge xup EXCLUDED <br>
bin = nbins+1; overflow bin <br>

virtual Double_t 	!GetBinContent (Int_t bin) const <br>
virtual Double_t 	!GetBinContent (Int_t bin, Int_t) const <br>
virtual Double_t 	!GetBinContent (Int_t bin, Int_t, Int_t) const <br>

Int_t TH1::FindBin 	( Double_t  x, Double_t  y = 0, Double_t  z = 0) <br>	
virtual Int_t FindBin(Double_t x); // Find bin number corresponding to abscissa x. <br> 

*gDirectory and subdirectories* <br>
You can change the directory of a histogram with the SetDirectory method. <br>
h->SetDirectory(newDir); <br>
*%RED%If the parameter is 0, the histogram is no longer associated with a directory!!!%ENDCOLOR%* <br>
h->SetDirectory(0);

In a ROOT session, you are always in a directory. The directory <br>
you are in is called the current directory and is stored in the global variable gDirectory.<br>

Make a pointer to a specific histogramme with gDirectory: <br>
<verbatim>TH1F *h = (TH1F*)gDirectory->GetList()->FindObject("myHist");</verbatim>

| gDirectory->pwd() | gDirectory points to the subdirectory. It prints the current directory location with pwd |
| gFile->pwd() | gFile points to the file's top directory, and prints the directory location with pwd |
| | |
| f1.cd(); | changes the current directory back to f1 |
| .pwd | CINT shortcut for gDirectory->pwd() |
| .ls | CINT shortcut for gDirectory->ls() |
| gROOT->cd() | Back to Rint:/, the topmost directory, and prints "(unsigned char)1" or "true" |
| | then gROOT->pwd() gives Rint:/ |
| gDirectory->ls("-d") | lists the objects on disk in the current directory |
| | |
| gDirectory->ls("-m") | list objects in memory |
| gDirectory->ls("-d") | list objects on disk |
| gDirectory->ls() | list objects in memory and then objects on disk |
| | |
| f->cd("Wed011003") | Change to subdirectory Wed011003 |
| gDirectory->GetFile() | From a subdirectory, get a pointer to the file containing the subdirectory |
TH1 *h; f->GetObject("Wed011003/histo;1",h) | histo from the top directory and the object will be in the top directory???? | 

*Create a sub-directory and return a pointer to the created directory.* <br>
Create first a/b/c and then a/b/d
<verbatim>
TFile * file = new TFile("afile","RECREATE");
file->mkdir("a");
file->cd("a");
gDirectory->mkdir("b");
gDirectory->cd("b");
gDirectory->mkdir("d");
</verbatim>

*Clone histogrammes* <br>
Make a complete copy of the underlying object. See [[https://root.cern.ch/doc/master/TH1_8cxx_source.html][TH1, line 2544]]<br>
<verbatim>
TObject* TH1::Clone(const char* newname) const
 {
    TH1* obj = (TH1*)IsA()->GetNew()(0);
    Copy(*obj); ..................


TH1F *h = (TH1F*)h1->Clone("h"); 
TH1F *hnew = (TH1F*)h->Clone("hnew") 
</verbatim>
If 'newname' is set, the copy's name will be set to that name.

*Fits to data, with error bars*
<verbatim>
i.e. a function defined in f1, a TF1 histogramme:
TF1 *f1 = new TF1("f1","[0]+[1]*x+[2]*x*x",90.,210.);

Some data, gr
gr = new TGraphErrors(np,volts,data,ex,ey);

Fit the data in gr, to the function in f1
 gr->Fit(f1);

Place the data points
gr->Draw("P");
</verbatim>


   * [[%ATTACHURL%/dynode-scan-fit.C][dynode-scan-fit.C]]
   * [[%ATTACHURL%/fit-protons-with-eta.C][fit-protons-with-eta.C]]

*Overlay a canvas on top of an existing PDF (pre-made plot)* <br>
[[https://root.cern.ch/phpBB3/viewtopic.php?t=7497][Rene's solution]], and $ROOTSYS/tutorials/image/img2pad.C

<verbatim>
void canvasimage() {
   //create a canvas with a picture (.png,.jpg,.gif, etc) in the background
   
   TImage *img = TImage::Open("rose512.jpg");  //put your own picture here
   TCanvas *c1 = new TCanvas("c1");
   img->Draw("x");
   
   //Create a transparent pad filling the full canvas
   TPad *p = new TPad("p","p",0,0,1,1);
   p->SetFillStyle(4000);
   p->SetFrameFillStyle(4000);
   p->Draw();
   p->cd();
</verbatim>


*Make Class* <br>
<verbatim>
root[] TFile f ("staff.root")
root[] f.ls()

returns:
TFile** staff.root
TFile* staff.root
KEY: TTree T;1 staff data from ascii file

Look at T, and make appropriate class
TTree *MyTree = T
T->Print();
T->MakeClass("MyClass")
returns:
Files: MyClass.h and MyClass.C generated from Tree: T

root[] MyTree->Scan();
will print the first 8 variables of the tree.
root[] MyTree->Scan("*");
will print all the variable of the tree.
Specific variables of the tree can be explicit selected by list them in column separated list:
root[] MyTree->Scan("var1:var2:var3");
will print the values of var1, var2 and var3. A selection can be applied in the second argument:
root[] MyTree->Scan("var1:var2:var3","var1==0");
will print the values of var1, var2 and var3 for the entries where var1 is exactly 0.
</verbatim>

| root -b | run in batch mode without graphics display |
| root -l | do not show the startup panel |
| gROOT->Reset() | Add at start of un-named scripts. Clears the variables, clears the global scope to the state |
| gROOT::GetListOf"TAB" | For other gROOT actions |
| TFile f("staff.root"); | read in file staff.root | 
| | TFile *_file0 = TFile::Open("root://castorcms//castor/cern.ch/user/n/ndefilip/Paper/data/roottree_leptons_DoubleElectron_Run2012A-22Jan2013-v1.root") |
| | Note the new formalism from Feb 2014, for castorcms |
| f->ls()  or f.ls() | list file contents, write out list of trees |
| T->Show(10); | show values of variables, 10th entry |
| T->Print() | Print list of variables/structure for tree T |
| T->Scan("Cost:Age:Children") | values for a list of leaves |
| T->StartViewer() | Get a viewer to look at the tree |
| T->Draw("Cost:Age") | plot cost versus age |
| TDatime t(unixTime_); | Convert unix time to ordinary time |
| t.Print(); | Print the time |
| | |
| UnZoom | rh click on axis concerned, in drop down menu, click on UnZoom |
| ZoomOut | rh click on axis concerned, in drop down menu, click on ZoomOut |
| | |
| | |
| The TPad::SetTicks() method specifies the type of tick marks on the axis. | Let tx=gPad->GetTickx() and ty=gPad->GetTicky(). |
| Axes | [[http://root.cern.ch/root/html/TGaxis.html][TGaxis to draw more axes]] |
| Axes | [[http://root.cern.ch/root/html/TGaxis.html#TGaxis:PaintAxis][Paint axis with chopt comments]] |
| tx = 1; | tick marks on top side are drawn (inside) |
| tx = 2; | tick marks and labels on top side are drawn |
| ty = 1; | tick marks on right side are drawn (inside) |
| ty = 2; | tick marks and labels on right side are drawn |
| tx=ty=0 |by default only the left Y axis and X bottom axis are drawn |
| Use TPad::SetTicks(tx,ty) to set these options. | See also the methods of TAxis that set specific axis attributes. |
| | If multiple color-filled histograms are drawn on the same pad, the fill area may hide the axis tick marks. | 
| | One can force the axis redrawing over all the histograms by calling: gPad->RedrawAxis() |
| | |
| TFile *f800 = new TFile("histo-run152847.root");  | read in root file |
| f800->ls(); | list contents of f800 |
| hadd | hadd newfile.root file_0.root file-1.root file-2.root file_3.root   to add histos to a file |
| | | 
| | |
| ifstream inFile ("cms_ecal_dcs_07_ECAL_HVM_0.csv"); | read in csv file |
| f800->cd("demo"); | go to histogram directory | 
| gDirectory->ls("-d"); | list the objects in the directory |
| h006->Draw(); | draw one of the histos |
| h167 = new TH2D ("h167"," ", 102, 0.,102., 102, 0.,102.); | new 2D histo |
| h65 = new TH1F ("h65","  ",100,0.,2.); | new 1D histo |
| h65->SetTitle(" EE+, Ratios for Va750/Va800, B=0T, 31Jan2011"); | Set title |
| hpx->GetXaxis()->SetTitle("Anode volts (Dynode = +600V) "); | set x-axis title |
| h167->Fill(i+1,j+1,1.0); | Fill histo |
| gPad->SetLogx(1) | Set log scale, x-axis |
| gPad->SetLogy(1) | Set log scale, y-axis |
| hpx->SetMaximum(5.); | set Max Y axis |
| hpx->Draw(); | Draw histo |
| hpx->Fit("gaus"); | FIT FIT, contents of hpx with a gaussian |
| hpx->Fit("pol5"); | FIT FIT, contents of hpx with a polynomial to power 5 (x**5) | 
| hpx->Fit("expo"); | FIT FIT, contents of hpx with an exponential | 
| hpx->Fit("landau"); | FIT FIT, contents of hpx to a landau | 
| gr3->Fit("expo"); | Fit an exponential to set of points gr3, where gr3 is a TGraph or TGraphErrors gr3(n,x,y,ex,ey); |
| gr3->Fit("pol0"); | etc |
| gStyle->SetOptStat(0); | no stats box |
| gStyle->SetOptStat(1); | to print fit values in the plot stats box |
| gStyle->SetOptFit(1011); | what fit values to print out |
| | mode = pcev (default = 0111) |
| | p = 1 print probability |
| | c = 1 print Chi-square/number of degrees of freedom |
| | e = 1 print errors (if e=1, v must be 1) |
| | v = 1 print name/values of parameters |
| ph700[i][j] = h006->GetBinContent(i+1,j+1); | get bin content |
| hsimple.C | generates hpx and hpxpy histos and writes them to hsimple.root |
| | from C: root tutorials |

Unix commands from root
   * to stream root output to a file use the > key as usual:
   * .x protfit.c > fit-out.txt

   * start with .! before a unix command, ie
   * .! ls

Bin content
   * ix = icentre = histo->Xaxis->GetBinCenter(bin id along x)
   * then getBinContent

To link and use other files do
   * .L  fn.C  where fn.C does not have outside brackets
   * ie File print1.h:
<verbatim>
// File print1.h:

int iy; // this will be a GLOBAL variable, accessible by other files !!!

void print1(int i, double ran1, int ib, double ran2, double probib, int icountib) {
  cout << " i= " << i << ", ran1 = " << ran1 << ", ib = " << ib << " ran2 = " 
  << ran2 << ", prob[ib] = " << probib << " icount[ib] = " << icountib << endl;  }

void prtchisq(double data[],int icount[],int bincount[],double chisqj, int bintot, int nevents, int ictot) {  cout << endl;
for(int i=0; i<5; i++) {
double chisqbin = ( (data[i]-double(icount[i]))**2) / icount[i] ;
cout << "i = " << i << ", bincount = " << bincount[i] << " data = " << data[i] << ", icount = " 
     << icount[i] << ", chisqbin = " << chisqbin << endl; }
cout << "bintot = " << bintot << ", nevents = " << nevents << ", ictot = " 
     << ictot << ", chisq = " << chisqj << "\n\n " << endl;}

</verbatim>

Don't include type defs in function call !!!!!!
<verbatim>
From  file: res-500-2p2.C

{
// if eta, lumiref,, lumi set for type in rescalc then DON'T do it here if have done .L rescalc.C before .x res-500-2p2.C!!!!!!!!!!!!!
//double eta = 2.2;
//double lumiref = 500.;
//double lumi = 3000.;
//double lumi = 500.;
eta=2.2; lumiref=500.; lumi=500;

rescalc(eta, lumiref, lumi);
// NOT NOT rescalc(double eta, double lumiref, double lumi); !!!!!!!!!!!!
</verbatim>

   * TABs:  typing f1->TAB will list all possible methods to do with f1, ie f1->Integral, -> Derivative,  -> !GetMaximum etc
   * In .tcshrc file put:   alias root "root -l"    to avoid startup panel
   * root[] TLine l
   * root[] l.Print()
   * root[] l.Print(); > test.log, Unix like I/O redirection (; is required before >)
   * root[] l.Dump(); >> test.log, Unix like I/O redirection to append onto existing file (; is required before >>)
   * root[] .class TLine, Use .class as quick help and reference

How to change text attributes
   * [[http://root.cern.ch/root/html/TAttText.html][Text attributes]]

How do I obtain a list of Branch or Leaf names?
   *  myTree->GetListOfBranches()->Print();
   *  myTree->GetListOfLeaves()->Print(); > leaf-list.txt

How do I get the Tree setup from a root file generated by someone else?
   * Use !MakeClass which will create the appropriate header file and class objects

How do I locate and fill the correct 1D or 2D bin, ie for EE ix, iy plots?
   * Use Int_t !FindBin(Double_t x, Double_t y = 0, Double_t z = 0), eg:
<verbatim>
Double_t ph = 45.63;
Int_t ix=36; 
Int_t iy=45;
Int_t nb = hxy->FindBin(Double_t(ix), Double_t(iy), 0); // returns a GLOBAL bin number
//SetBinContent(Int_t bin, Double_t content)
hxy->SetBinContent(nb, ph);
</verbatim>  

How to print a number and/or a string of text on the plot:
<verbatim>
Double_t dg = 0.;
dg=100*(fit[1]+2*fit[2]*v )/(fit[0]+fit[1]*v+fit[2]*v*v);
char textToPlot[80];
sprintf(textToPlot,"%5.3f%%",dg);   // %% prints the % sign
cout << textToPlot  << endl;
TLatex t;
   t.SetTextAlign(22);
   t.SetTextSize(0.05);
   t.DrawLatex(800,0.12,textToPlot);
   t.DrawLatex(800,0.105,"per volt");
</verbatim>

How to get run number etc into the histogramme title:
<verbatim>
  string run;
  string side;
  string volts;
  run = iConfig.getUntrackedParameter<string>("runnum");
  side = iConfig.getUntrackedParameter<string>("EEside");
  volts = iConfig.getUntrackedParameter<string>("volts");
  TString tsrun, tsside, tsvolts, tsinfo;
   tsside = side;
   tsvolts = volts;
   tsrun = run;
   tsinfo = "Run " + run + ", " + side + ", " + volts;
h901 = fs->make<TH2D>("h901", tsinfo + ", digiph (ADC counts) versus rechit ph (ADC counts)",
100,-0.5,1000., 100,-0.5, 1000. );

******** and in config file:
run = ['158931','EE+','400/200']
process.demo = cms.EDAnalyzer('HVAnalyzer',
                runnum = cms.untracked.string(run[0]),
                EEside = cms.untracked.string(run[1]),
                volts = cms.untracked.string(run[2])
)
</verbatim>

---++ FAQ sites and How to's

[[http://www-glast.slac.stanford.edu/software/root/howto/faq.htm][Stanford]] [[http://hadron.physics.fsu.edu/~skpark/document/ROOT/root_beginers/][skpark]] [[http://minos.phy.bnl.gov/~bviren/cern/root/rug/][MINOS-viren]]

From Jpark - Tutorial Day 2
To find all methods associated with a class, command line completion with TAB.
   * Most methods which change an object begin "Set…"
   * Most methods which give information about an object begin "Get…"
   * TAB use, typing f1->TAB will list all possible methods to do with f1, ie f1->Integral, -> Derivative,  -> GetMaximum etc
Code
   * go to ROOT reference guide - > list of classes and key word search
Destructors
   * cannot access object directly, use: delete toto;    where toto is a pointer to the object
Methods  
   * Looking for a method, ie Divide     -> could be a parent method, ie in the public TPad area, a parent of TCanvas
               -> since TCanvas does not have a Divide method, the one in TPad is used
Finding 'lost' objects ! 
   * ROOT keeps lists of objects allowing them to be found easily
   * Go to ROOT Object Browser -> Click on 'root',  click on Canvases, get window list
   * Each object has a unique name
Use a pointer found with gROOT   or - if you know the address of the object, you could use a pointer, ie:
   * gROOT->GetListOfCanvases()->FindObject("c1");
   * gROOT is a GLOBAL pointer, with the address of the root folder of the folder tree.
   * gROOT points to an object of the class TROOT.
If you aren't sure which folder to look in, you can recursively search through all the folders:
   * Instead of gROOT->GetListOfCanvases()->FindObject("c1");
   * Do            gROOT->FindObject("name");
This is the MAGIC FORMULA which allows to find (nearly) any object anywhere anytime. You'll use it all the time!!
All you have to do now is put the address in the appropriate pointer and use it:
   * ClassName* toto = (ClassName*) gROOT->FindObject("nom");    (Have to respecify the class of the object we hope to find here)
   *  Example: we look for canvas "c1" and wipe it clean:
   *     TCanvas* c1_ptr = (TCanvas*) gROOT->FindObject("c1");
   *    c1_ptr->Clear();
Testing if an object exists: gROOT-> FindObject("h1")   
   * If it exists, get ie, (const TObject*)0xaffa198
   * If not,                  (const TObject*)0x0            function returns an address equal to zero
To be rigorous, you should always test the value of a pointer before trying to use it, ie
   * TH1F* p=(TH1F*)gROOT->FindObject("hh")
   *  p->Draw()

---++ Tutorials
| [[http://root.cern.ch/root/html/tutorials/index.html][ROOT tutorials]] |  
| [[http://root.cern.ch/root/html/tutorials/hist/index.html][Histo tutorials]] |
| [[http://root.cern.ch/root/html/tutorials/hist/h1draw.C.html][Canvas setup instructions with picture]] |
| [[https://twiki.cern.ch/twiki/pub/Main/GeneralComputingNotes/ROOT_for_beginners_Day1.pdf][ROOT_for_beginners_Day1]] |
| [[https://twiki.cern.ch/twiki/pub/Main/GeneralComputingNotes/ROOT_for_beginners_Day2.pdf][ROOT_for_beginners_Day2]] |
| [[https://twiki.cern.ch/twiki/pub/Main/GeneralComputingNotes/ROOT_for_beginners_Day3.pdf][ROOT_for_beginners_Day3]] |
| [[https://twiki.cern.ch/twiki/pub/Main/GeneralComputingNotes/ROOT_for_beginners_Day4.pdf][ROOT_for_beginners_Day4]] |
| [[https://twiki.cern.ch/twiki/pub/Main/GeneralComputingNotes/ROOT_for_beginners_Day5.pdf][ROOT_for_beginners_Day5]] |

---++ Classes
[[http://root.cern.ch/root/html/ClassIndex.html][Class index]]

| [[http://root.cern.ch/root/html524/ClassIndex.html#idx44][TPad]] | Click on Tpad in middle of screen to link to the Tpad class |
| [[http://root.cern.ch/root/html/TFile.html][TFile]] | Open a root file <br> It is recommended to specify fname1 as "<file>.root". The suffix ".root" |
| [[https://root.cern.ch/doc/master/classTFile.html][classTFile.html]] | NEW or CREATE: Create a new file and open it for writing <br>if the file already exists the file is not opened. |
| | RECREATE: Create a new file, if the file already exists it will be overwritten. |
| | Syntax: TFile * file = new TFile("afile","RECREATE");
| | UPDATE: Open an existing file for writing. If no file exists, it is created. |
| | READ: Open an existing file for reading (default). |
| | If option = "" (default), READ is assumed. The file can be specified as a URL of the form:<br>file:///user/rdm/bla.root or file:/user/rdm/bla.root<br> |
| file->Write(); | Save all histograms in memory to file |
| | |
| | The file can also be a member of an archive, in which case it is specified as:<br>multi.zip#file.root or multi.zip#0<br>which will open file.root which is a member of the file multi.zip archive or member<br>from the archive. See [[https://root.cern.ch/doc/master/classTArchiveFile.html][TArchiveFile class]] | 
| | TFile and its remote access plugins can also be used to open any file, i.e. also non ROOT files, using: file.tar?filetype=raw |
| | |
| [[http://root.cern.ch/root/html524/TStyle.html][TStyle]] | This class lists the functions to set the following object attributes:<br>Canvas  - Pad   - Histogram axis  - Lines  - Fill areas   - Text  - Markers  - Functions  - Histogram Statistics and Titles,<br>TStyle::%RED%SetLabelColor%ENDCOLOR% <br>%RED%SetLabelOffset%ENDCOLOR%(Float_t offset=0.005, Option_t *axis="X"); <br>%RED%SetTitleFont%ENDCOLOR%(Style_t font=62, Option_t *axis="X"); <br>%RED%SetTitleX%ENDCOLOR%(Float_t x=0); void !SetTitleY(Float_t y=0.985) |
| | |
| [[http://root.cern.ch/root/html/TCanvas.html][TCanvas]] | TCanvas construct and destruct syntax <br>[[http://root.cern.ch/root/html/src/TCanvas.cxx.html][ !TCanvas source code]], <br>TCanvas.cxx.html <br> |
| | |
| [[http://root.cern.ch/root/html524/TPad.html][TPad]]* | The !TPad class is the %RED%most important graphics class%ENDCOLOR% in the ROOT system.<br>[[http://root.cern.ch/root/html524/src/TPad.cxx.html][ TPad source code ]], <br>ie TPad::TPad(const char *name, const char *title, Double_t xlow, Double_t ylow, Double_t xup, Double_t yup, Color_t color, Short_t bordersize, Short_t bordermode) <br>:TVirtualPad(name,title,xlow,ylow,xup,yup,color,bordersize,bordermode) |
| [[http://root.cern.ch/root/html524/TAttPad.html][TAttPad]] | Manage TPad attributes, referenced by TStyle, ie %RED%SetMargin%ENDCOLOR%(Float_t left, Float_t right, Float_t bottom, Float_t top) etc |

---++ Examples
[[http://root.cern.ch/root/html/TStyle.html#TStyle:SetTitleOffset][Example of the !SetTitleOffset member]]
<verbatim>void SetTitleOffset (Float_t offset = 1, Option_t* axis = "X")
Specify a parameter offset to control the distance between the axis and the axis title.
offset = 1 means : use the default distance
offset = 1.2 means: the distance will be 1.2*(default distance)
offset = 0.8 means: the distance will be 0.8*(default distance)
axis specifies which axis ("x","y","z"), default = "x"
if axis="xyz", set all 3 axes
</verbatim>

[[http://root.cern.ch/root/html/TStyle.html#TStyle:SetTitleSize][Example of the !SetTitleSize member ]]
<verbatim>void SetTitleSize (Float_t size = 0.02, Option_t* axis = "X")
 if axis =="x"  set the X axis title size
 if axis =="y"  set the Y axis title size
 if axis =="z"  set the Z axis title size
 *Any other value of axis will set the PAD title size!!!*
if axis="xyz" set all 3 axes
</verbatim>

---++ Usage
| *Comment* | *ROOT* |
| Most common error, no ";" at end of line | This MAY NOT cause a compiler error and so is most frustrating! | 
| ==Canvases== | A canvas has a default pad which has the name of the canvas itself |
| TCanvas(const char* name, const char* title, Int_t wtopx, Int_t wtopy, Int_t ww, Int_t wh) | Set pos'n on screen and size |
| TCanvas(const char *name, const char *title, Int_t ww, Int_t wh) | Set size, random position on screen |
| TCanvas(const char* name, const char* title = "", Int_t form = 1) | Sets up a canvas, of size/pos for 5 forms, 1-5 |
| TCanvas(const char *name, Int_t ww, Int_t wh, Int_t winid) | Create an embedded canvas |
| ==TLine * l;==| define a pointer to a line object, called l |
| l = new TLine(x1,y1,x2,y2); l->SetLineStyle(2); l->Draw(); | l is new so stays on heap??, line style 'dash' |
| ==TArrow * ar;== | define a pointer to an arrow object, called ar |
| ar = new TArrow(200, 0.08, 200, 0.03, 0.01, ">"); ar->Draw(); | x1, y1, x2, y2, size, "arrow head", also "&lt;", "&#124;&gt;", "&lt;&#124;", "&lt;&gt;", "&lt;&#124;&gt;"  |
| char textToPlot[80]; dg = 0.0148; | printing text and values of variables to the canvas using latex |
| sprintf(textToPlot,"%5.4f%%",dg); cout << textToPlot  << endl; | using sprintf to combine text and variable, note the format spec %5.4f and the percentage sign enterred with %% |
| ==TLatex t;== | t.SetTextAlign(22); t.SetTextSize(0.05); | 
| ^ | t.SetTextAlign(Align); horiz 1=left, 2=centre, 3=rt, vert 1=bott, 2=centre, 3=top, ie Align=23 |
| ^ | t.DrawLatex(195,0.105,textToPlot);  t.DrawLatex(195,0.09,"per volt"); |
| ==Histo titles etc== | f1->SetTitle("Dynode scan, anode 800V, 3.8T"); | 
| ^ |f1->GetXaxis()->SetTitle("Anode-Dynode voltage (V)");  x-axis title |
| ^ |f1->GetXaxis()->CenterTitle(); places x-axis title at centre across plot |
| ^ |f1->GetYaxis()->SetTitle("VPT response (arb. units)");  y-axis title |
| ^ |f1->GetYaxis()->CenterTitle();  places y-axis title at centre along y |
| ^ |f1->GetYaxis()->SetRangeUser(0.894,1.01);  set user range for the Y axis |
| ^ |f1->GetXaxis()->SetRangeUser(90.,210.);  set user range for the X axis |
|gStyle->SetTickLength(0.02,"y"); | |
|gStyle->SetTickLength(0.05,"x"); | |
|gStyle->SetTitleSize(0.05,"x"); | |
|gStyle->SetTitleSize(0.05,"y"); | |
|gStyle->SetTitleOffset(1.1,"y"); | y-axis title, distance from y axis |
|gStyle->SetTitleOffset(1.,"x"); | x-axis title, distance from x axis |
|gStyle->SetTitleAlign(13); |histo title position along x, global set for all histos following |
|gStyle->SetPadBottomMargin(0.15); | Set distance from histo x-axis to bottom of pad |
|<verbatim>gROOT->ProcesssLine(".x myprog.C"); </verbatim>| to execute a script inside another script  |
|max 20 value, Set max value on Y axis for 1D hist #20  |h20->SetMaximum(value);    |
|min 20 value, Set min value on Y axis for 1D hist #20  |h20->SetMinimum(value);    |
|Get max entries from histo h1   |h1->GetMaximum();    |
|Get min entries from histo h1   |h1->GetMinimum();    |
|histo/del 10         |h10->Delete();  |
|Increase # of points plotted along a fn, f1 (default is 100 only) |f1.SetNpx(200);    |
|h/fill,     |h1->Fill(x); (note the capital F!)   |
|Set y-axis range on a 2D function plot  |f1->GetYaxis()->SetRangeUser(min, max);    |
|Data from fits   |func->GetParameter(0);   |
|Data from fits   |func->GetParameter(1);   |
|Data from fits   |func->GetParameter(2); etc   |
|Error on data from fits   |func->GetParameterError(0); etc   |
| Set up a function, transfer the coefficients, draw | TF1 *f1 = new TF1("f1","[0]+[1]*x+[2]*x*x",360.,860.); x from 360 to 860 |
| ^ | f1->SetParameters(fit[0],fit[1],fit[2]); f1->Draw(); |
| ^ | f1->SetParameter(0,value_first_parameter); |
| ^ | f1->SetParameter(1,value_second_parameter); |
| Line characteristics | f1->SetLineColor(2); 1=blk 2=%RED%red%ENDCOLOR% 3=%GREEN%bright grn%ENDCOLOR% 4=%BLUE%bright blue%ENDCOLOR% 5=%YELLOW%yell%ENDCOLOR% 6=%PINK%pink%ENDCOLOR% 7=%AQUA%aqua%ENDCOLOR% 8=%GREEN%grn%ENDCOLOR% 9=%BLUE%blue%ENDCOLOR%  |
| ^ |f1->SetLineWidth(2); // range from 1-15 |
| ^ |f1->SetTitle("Anode scan, anode-dynode 200V, 0T"); |
| ^ |int_t lwid = 0; lwid = f1->GetLineWidth(); |
| ^ |int_t lcol = 0; lcol = f1->GetLineColor(); |
|||
|Un-named scripts | must start and end with {....} |
|          | with #include statements inside the { |
|          | All statements executed in the interpreters global scope |
|          | Variables are in the global scope and are available on the cmd line, even after script has done executing |
|gROOT->Reset() | place at top of un-named script, to reset global environment/clear the variables         | 
|                             | calls destructor of objects, if object created on stack |
|                             | If object was created on the heap, with 'new', it is not deleted  |
|                             | Must call the destructor explicitly (or get Memory leak warnings) |
|Named scripts | #include statements, then function statements, no {....} from start to end |
|          | Objects are created on the stack, and are deleted upon exit, including histos |
|          | To avoid histo dissappearing, create it on the heap using 'new' |
|          | Histos and trees auto deleted when the current directory is closed |
| ie file script.C: | |
| #include <iostream.h> | |
| int run() | |
| {cout << " Hello" << endl; return 0;  } | |
| root[0] .L script.C | |
| root[1] run () | |
<br>
<br>
<br>

---++  Setting up Root, 23.9.09
Success incorporating ROOTSYS into PATH in tcsh shell.
   *  setenv ROOTSYS /afs/cern.ch/na49/library.4/...../root
   *  setenv PATH $PATH":$ROOTSYS"   appends the ROOTSYS string, with a colon, to the rest of the PATH string set.

---++ Trip ups and Warnings

28 Jul 2014 Problems, in HXX work, with statement </br>
hIso_3->Scale(1./hIso_3->Integral()); </br>
Need to separate out with Double_t myintegral = 0.; myintegral = hMZ1_3->Integral();  hMZ1_3->Scale(1./myintegral);

Memory leakage warnings from ROOT - happens if creating same histo again, ie running .C file again. Pointers to original histos are lost -> old histos in inaccessible memory space. Change directory to zero. Changes ownership of histos from ROOT to me. Can then delete histos. However ROOT manages all these memory leaks so not an issue. 
<br>
<br>
<br>
---++ Paw to Root
[[http://cern.ch/cms-EE-info/Paw-canvas-to-ROOT.mht][paw-to-root-canvas]]
<br>
<br>
<br>

-- Main.DavidCockerill - 05-Nov-2009

   * [[%ATTACHURL%/dynode-scan-fit.C][dynode-scan-fit.C]]: dynode-scan-fit.C

   * [[%ATTACHURL%/Tree-test.C][Tree-test.C]]: Tree-test.C</verbatim>

   * [[%ATTACHURL%/basic.dat][basic.dat]]: basic.dat</verbatim>

   * [[%ATTACHURL%/Tree-vpts-types-in-dat-file.c][Tree-vpts-types-in-dat-file.c]]: Tree-vpts-types-in-dat-file.c</verbatim>

   * [[%ATTACHURL%/basic-vpts-with-types.dat][basic-vpts-with-types.dat]]: basic-vpts-with-types.dat</verbatim>

   * [[%ATTACHURL%/basic-vpts-john-wood-linux-data.dat][basic-vpts-john-wood-linux-data.dat]]: basic-vpts-john-wood-linux-data.dat</verbatim>

   * [[%ATTACHURL%/fit-protons-with-eta.C][fit-protons-with-eta.C]]: fit-protons-with-eta.C</verbatim>

   * pict1_TColor_002.png: <br />
     <img src="%ATTACHURLPATH%/pict1_TColor_002.png" alt="pict1_TColor_002.png" width="396" height="372" /></verbatim>
Attachments
Topic attachments
I	Attachment	History	Action	Size	Date	Who
c	Tree-test.C	r1	manage	3.0 K	2015-06-02 - 13:34	DavidCockerill
c	Tree-vpts-types-in-dat-file.c	r1	manage	3.7 K	2015-06-04 - 11:15	DavidCockerill
dat	basic-vpts-john-wood-linux-data.dat	r1	manage	2.4 K	2015-06-04 - 11:15	DavidCockerill
dat	basic-vpts-with-types.dat	r1	manage	3.1 K	2015-06-04 - 11:15	DavidCockerill
dat	basic.dat	r1	manage	0.1 K	2015-06-02 - 13:34	DavidCockerill
c	dynode-scan-fit.C	r1	manage	4.0 K	2013-12-02 - 10:38	DavidCockerill
c	fit-protons-with-eta.C	r1	manage	2.8 K	2015-06-17 - 13:54	DavidCockerill
png	pict1_TColor_002.png	r1	manage	55.0 K	2019-09-26 - 10:49	DavidCockerill
Topic revision: r121 - 2021-10-17 - DavidCockerill
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