I want to get the root of a fit function in a specific interval. I want to ignore this event if the interval does not contain a root.
But I can’t know whether there is a root in the interval.
I tried the following code:
Double_t r = fun->GetX(0,1,9); cout << r << endl;
The output is:
Info in <ROOT::Math::BrentMethods::MinimStep>: Grid search failed to find a root in the interval Info in <ROOT::Math::BrentMethods::MinimStep>: xmin = 1 xmax = 9 npts = 100 Error in <ROOT::Math::BrentRootFinder>: Interval does not contain a root Error in <TF1::GetX>: [1.000000,9.000000] is not a valid interval nan
It seems that TF1::GetX() returns a “nan”, but I can’t judge it by
if (r == nan) Output: ROOT_prompt_3:1:2: error: invalid operands to binary expression ('Double_t' (aka 'double') and 'double (const char *) throw()') r==nan
I have also tried “try-catch method”, but TF1::GetX() doesn’t throw any exception.