myplotROOT

Class: myplot.C

Plotting example: plot_test.C

Example

$ ./plot_test test.root 
~ Reading histograms from file test.root
c14_nhits
be7_nhits
po210_nhits
~ Drawing
c14_nhits
be7_nhits
po210_nhits
~ Saving canvas to file test_plot.root
Info in <TCanvas::Print>: pdf file test_plot.root.pdf has been created

Produces:

How to compile `plot_test.C`

Compile via

g++ -Wall -O2 -o plot_test plot_test.C `root-config --cflags --glibs`;

Tip: add shortcut to .bashrc

compileit(){
    g++ -Wall -O2 -o ${1%.*} $1 `root-config --cflags --glibs`;
}

And use compileit plot_test.C to create plot_test

How to use `myplot.C`

Use in a macro

#include "myplot.C"

int main(){
    Myplot* p = new Myplot("test.root", false, true); 

    p->DrawHistos();
    
    p->SetLabels("nhits", "");
    p->SaveCanvas("test_plot.root", true);
}

(check out plot_test.C for more)

Reading histograms from file

Say you collect several histograms that you want to plot in one root file called test.root

TFile**         test.root
 TFile*         test.root
  KEY: TH1D     c14_nhits;1     final_nhits_pp
  KEY: TH1D     be7_nhits;1     final_nhits_pp
  KEY: TH1D     po210_nhits;1   final_nhits_pp

You simply give this file to Myplot:

Myplot* p = new Myplot("test.root");

Optional arguments are

scale (true|false) scale the histograms to the same area (default false)
yscale (true|false) set Y axis to log scale (default true)

E.g.

Myplot* p = new Myplot("test.root", false, true);

Adding histograms in separate files

If you want to read the histograms from different files, you can initiate an empty plot

Myplot* p = new Myplot();

And then add the histograms from the files, for example

for( < loop over files ){
    TFile f(<name>);
    TH1D* h = (TH1D*) f->Get(<histo name>);
    p->AddHisto(h);
}

Drawing

To draw the histograms, do

p->DrawHistos()

While reading the histos, Myplot has figured out the minimum and maximum values for x and y axes, and will create a Frame based on those values so that all the histograms fit in it. In case you want your own X and Y limits, set them before calling DrawHistos() with p->SetXlim(x1,x2) and/or p->SetYlim(y1,y2).

When drawing, this function will automatically create a legend with different colours and adjust the width of the legend based on the length of the label. The label of each histogram is its title.

You can set X and Y labels and a title via:

p->SetLabels("x label", "y label");
p->SetTitle("title");

Saving the plot

To save the plot, use the function p->SaveCanvas().

If you drew from one file, and don't pass any arguments to this function, it will automatically save the canvas with the plot to a file called test.root.out (i.e. your original input file plus ".out").

If you added histos manually from many files, or want a different name, you can pass it to the function. Also, if you want to save a PDF of the plot, you can set the corresponding bool to true (which is false by default):

p->SaveCanvas("name.root", true);

Drawing lines

If you want to draw lines on the plot, you can do it via:

TLine* line = new TLine(...);
p->AddLine(line);
p->DrawLines();

sagitta42/myplotROOT