Re: TF3::GetHistogram() seg violation

From: Lorenzo Moneta <Lorenzo.Moneta_at_cern.ch>
Date: Wed, 30 Mar 2011 13:26:16 +0000

Hi,

 To fill a 3D histogram from a TF3 function you can do something like this

{

   TF3 * f3 = new TF3("f3","x*x+y*y+z");    f3->Draw();
   gPad->Update(); // this forces the creation of the histogram    TH3 * h3=(TH3*) f3->GetHistogram();

   double xv[3];
   f3->InitArgs(xv, f3->GetParameters());    for (int i=1;i<=h3->GetNbinsX();i++) {

      xv[0] = h3->GetXaxis()->GetBinCenter(i);
      for (int j=1;j<=h3->GetNbinsY();j++) {
         xv[1] = h3->GetYaxis()->GetBinCenter(j);
         for (int k=1;k<=h3->GetNbinsZ();k++) {
            xv[2] = h3->GetZaxis()->GetBinCenter(k);
            int bin = h3->GetBin(i,j,k);
            h3->SetBinContent(bin,f3->EvalPar(xv,f3->GetParameters()) );
         }
      }

   }

   h3->Draw("ISO");
}

Lorenzo

On Mar 30, 2011, at 2:58 PM, Serhiy Senyukov wrote:

> Thank you for your suggestion Oliver. However it is not the thing I would like to do.
> What I really need is to translate 3D function into reasonable histogram. Final goal is to visualize the original 3D function.
> 

>> -----Original Message-----
>> From: Olivier Couet
>> Sent: Wednesday, March 30, 2011 2:44 PM
>> To: Serhiy Senyukov
>> Cc: Olivier Couet; roottalk (Mailing list discussing all aspects of the
>> ROOT system.)
>> Subject: RE: [ROOT] TF3::GetHistogram() seg violation
>>
>>
>>
>> I think the TH3 ib that case is only used to draw the frame and remains
>> empty. You should try to do something like that:
>>
>> {
>> TH3D *earth = new TH3D("earth", "earth", 100, -1., 1., 100, -1.,
>> 1.,100, -1., 1.);
>> double phi=0., cos_theta=0., theta=0.;
>> for(int i=0; i<100; i++){
>> phi=gRandom->Uniform(0., 6.28);
>> cos_theta=gRandom->Uniform(0., 1.);
>> theta=acos(cos_theta);
>> earth->Fill(cos(phi)*sin(theta), sin(phi)*sin(theta),
>> cos_theta);
>> }
>> TCanvas *c1 = new TCanvas("c1", "c1",1);
>> earth->SetMarkerStyle(4);
>>
>> earth->Draw("box");
>> }
>>
>>
>>
>> Org: CERN - European Laboratory for Particle Physics.
>> Mail: 1211 Geneve 23 - Switzerland Mailbox:
>> J25910
>> E-Mail: Olivier.Couet_at_cern.ch Phone: +41
>> 22 7676522
>> WWW: http://cern.ch/Olivier.Couet/ Fax: +41
>> 22 7670300
>>
>> On Wed, 30 Mar 2011, Serhiy Senyukov wrote:
>>

>>>> As you see I get 100 .
>>>> I am using the trunk
>>> [Serhiy Senyukov] As far as I can see from your code you are getting

>> 100 evaluating the function itself. Contrary I get zero by asking the
>> bin content of the histogram derived from the function.

>>> 
>>>>>> I do not see what you describe here.
>>>>> [Serhiy Senyukov] Ok. I have found the reason for the first issue.
>>>> There
>>>>> were parameters missing in the declaration of the 3D function.

>> However

>>>>> the bin content of the produced histogram is always zero.
>>>>> 
>>>>> Regards,
>>>>> Serhiy.
>>>>> 
>>>>>> root [0] .x ser.C
>>>>>> Processing ser.C...
>>>>>> Test function3 test = 100
>>>>>> Info in <TCanvas::MakeDefCanvas>:  created default TCanvas with

>> name

>>>> c1
>>>>>> 
>>>>>> The macro is:
>>>>>> 
>>>>>> Double_t test(Double_t *x, Double_t *par)
>>>>>> {
>>>>>>     return 100;
>>>>>> }
>>>>>> 
>>>>>> void ser(Int_t nPoints=5){
>>>>>>    TF3* test_f3=new TF3("test_f3",test,0,10,0,10,0,10,2);
>>>>>>    test_f3->SetParameters(1,2);
>>>>>>    test_f3->SetNpx(nPoints);
>>>>>>    test_f3->SetNpy(nPoints);
>>>>>>    test_f3->SetNpz(nPoints);
>>>>>> 
>>>>>>    cout<<"Test function3 test = "<<test_f3->Eval(5,5,5)<<endl;
>>>>>> 
>>>>>>    test_f3->Draw();
>>>>>>    TH3F* test3_hist=(TH3F*)test_f3->GetHistogram();
>>>>>> }
>>> 
>>> 
> 

Received on Wed Mar 30 2011 - 15:26:21 CEST