Fix PDF returned by some function

[Youying]

Hi,

For now, I have some function which can return one PDF. For example,

RooAbsPdf* myPdf = some_function();

How do I fix this pdf (called myPdf) if I don’t know any information of parameters inside “myPdf” ? Namely, can any member function or tricky method do

myPdf -> “fix()” ?

Thanks

[ganis]

Dear Youying,

By ‘fix’ you mean fixing parameters?
Can you please provide a detailed example of what you want achieve?

G Ganis

[Youying]

Hi Ganis,

Yes, ‘fix’ means “fix all parameters inside this pdf returned by some function” to avoid these parameters floating. Because some pdf returned by some function can not be fixed by using

param1.setConstant(kTrue);
…,

can any other idea achieve this if we don’t use “setConstant()” ?

Thanks
Youying

[moneta]

Hi,

param1.setConstant(kTrue) should fix the parameter of your PDF. If it does not work it means the reference you have to the RooRealVar points to a copy of the one stored in the PDF.
A possible solution is in this case to retrieve it directly from the pdf, by doing for example

auto vars = pdf->getVariables(); auto p = (RooRealVar*) vars->find(param1.getName() ); p->setConstant(kTrue); delete vars;

Lorenzo

[Youying]

Nice!

Thank you very much, Lorenzo!

Youying