Re: [ROOT] Using a declared variable in a root command line

From: Rene Brun (Rene.Brun@cern.ch)
Date: Mon Mar 18 2002 - 14:14:08 MET


Hi Reinhardt,

Modify your code as indicated below.

Rene Brun

Reinhardt Chamonal wrote:
> 
> Hi the experts,
> 
> First that's going be a very very basic question. I had a look at
> various examples around but I am stuck and frustrated. (I am started at
> Root)
> What I would like to do is a little simple script to take a number and
> then
> plot the histogram corresponding to this number
> Here is what I do:
> 
> #include <iostream.h>
> 
> int show(Int_t nb) {
>   gROOT->Reset();
>   c1 = new TCanvas("mapmt","MAPMTs",10,40,800,600);
>   TFile *f = new TFile("r99.root"); //<================
    //use new, otherwise when closing the file, hist will be destroyed
>   //TFile *f = new TFILE("r99.root");
>   gPad->SetLogy();
>   TH1F *boundary = new TH1F("boundary","Channel Signal",500,-0.5,250.5);
    TString cut = "pdid==0 && pixid==";
    cut += nb;
>   h10->Draw("norm>>+boundary","cut);
>   c1->Update();
>   //return 0;
> 
> }
> 
> so calling show(2) should draw the  histogram cooresponding to pixid=2
> when calling
> h10->Draw("norm>>+boundary","pdid==0 && pixid==nb");
> where I put my variable nb. It obviously doesn't like it certainly because
> of the "". What is the correct declaration in this case ?
> Can anybody indicate me an example where this is used ?
> 
> Also as running my script without nb, (with the number instead) works but
> the histogram shows up and then disappears... :(
> I read  something about the heap.. (as my histogram boudary with my
> personnal boundaries is declared as new). Is it the case ? What can I do
> to let it stay ?
> 
> Cheers.
> 
> ------------------------------------------------------------
>  Reinhardt CHAMONAL            The University of Edinburgh
>                                Dept. of Physics & Astronomy
>  email: chamonal@ph.ed.ac.uk   King's Buildings, JCMB, 5301
>                                Mayfield Road
>  phone: +44-131-650 5307       Edinburgh, EH9 3JZ
> 
>  web: http://www.ph.ed.ac.uk/~chamonal/
>       http://www.reuh.fr.st
> ------------------------------------------------------------



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