AbstractFit

Description

Both response and resolution fits needs to test different fit ranges and parameter configurations.

#include <fit.h>

Inheritance diagram for AbstractFit:

Collaboration diagram for AbstractFit:

Public Member Functions
virtual bool	good () const

Public Attributes
const std::unique_ptr< TH1 > &	h
std::uint32_t	status
std::ostream &	cout
double *	p
double *	e
std::unique_ptr< TF1 >	f
std::optional< double >	chi2ndf
std::optional< double >	chi2ndfErr
std::pair< float, float >	interval

Protected Member Functions
	AbstractFit (const unique_ptr< TH1 > &h, ostream &cout, int npars)
virtual	~AbstractFit ()
void	fit (std::pair< float, float >, const char *)
virtual void	Write (const char *name)

Constructor & Destructor Documentation

AbstractFit()

AbstractFit ( const unique_ptr< TH1 > &  h, ostream &  cout, int  npars  )

inlineprotected

                                                                     :
        h(h), status(0), cout(cout),
        p(new double[npars]), e(new double[npars])
    { }

~AbstractFit()

virtual ~AbstractFit ( )

inlineprotectedvirtual

    {
        for (int i = 0; i < f->GetNpar(); ++i) {
            if (isfinite(p[i])) continue;
            const char * what = Form("Fit parameter %d is not finite", i);
            BOOST_THROW_EXCEPTION( std::runtime_error(what) );
        }
        delete p;
        delete e;
    }

Member Function Documentation

fit()

void fit ( std::pair< float, float >  range, const char *  fitName  )

protected

Perform fit in given range. Starting parameters are always taken from the members, which are expected to provide the so-far best parameter estimation. The parameters and the range are overriden in case of improvement of fit performance.

Link to ROOT TH1::Fit() doc

Todo:

https://stackoverflow.com/questions/37385560/c-redirect-or-disable-stdio-temporarily to avoid this dumb arrow

Todo:

E: use Minos for error estimations

{
    using namespace std;
 
    // reinitialise the params to the best known fit
    f->SetParameters(p);
    f->SetParErrors (e);
    f->SetRange(range.first, range.second);
    for (int i = 0; i < f->GetNpar(); ++i) {
        double m, M;
        f->GetParLimits(i,m,M);
        if (p[i] >= m && p[i] <= M) continue;
        cerr << orange << setw(2) << i
                       << setw(10) << m
                       << setw(10) << M
                       << setw(10) << p[i]
                       << def << '\n';
    }
 
    // run the fit
    TFitResultPtr result = h->Fit(f.get(), "QS0NRE");
    // Q: quiet
    // S: return smart pointer to fit restult (automatic conversion to integer provides fit status)
    // 0: do not draw
    // N: do not store graphics
    // R: use fit range
 
    // get result
    double currentChi2ndf = f->GetChisquare()/f->GetNDF();
 
    bool success = result >= 0 && result % 10 == 0 && currentChi2ndf < 10000;
    //  status = migradStatus + 10*minosStatus + 100*hesseStatus + 1000*improveStatus.
    //  TMinuit returns 0 (for migrad, minos, hesse or improve) in case of success and 4 in case of error (see the documentation of TMinuit::mnexcm).
    //  For example, for an error only in Minos but not in Migrad a fitStatus of 40 will be returned.
    //  Minuit2 returns 0 in case of success and different values in migrad,minos or hesse depending on the error.
    //  See in this case the documentation of Minuit2Minimizer::Minimize for the migrad return status,
    //                                        Minuit2Minimizer::GetMinosError for the minos return status,
    //                                    and Minuit2Minimizer::Hesse for the hesse return status.
 
    bool improvement = !chi2ndf || abs(currentChi2ndf-1) <= abs(*chi2ndf-1);
 
    cout << h->GetTitle() << " with " << bold << fitName << normal << " in ["
         << fixed << setprecision(2) << range.first << "," << range.second << "]: " << defaultfloat
         << (success ? (improvement ? green : orange) : red) << *this
         << fixed << setprecision(3) << setw(15) << currentChi2ndf << defaultfloat
         << "\t(status = " << (int) result << ")" << def << endl;
 
    // skip if the new attempt isn't improving the performance
    if (!success || !improvement) return;
 
    // at this stage, we can consider that the fit has improved, 
    // therefore we save the current parameter estimates
    chi2ndf = currentChi2ndf;
    chi2ndfErr = sqrt(2./f->GetNDF());
    for (int i = 0; i < f->GetNpar(); ++i) {
        p[i] = f->GetParameter(i);
        e[i] = f->GetParError (i);
    }
    interval = range;
}

good()

virtual bool good ( ) const

inlinevirtual

Reimplemented in ResponseFit.

{ return chi2ndf && status; }

Write()

virtual void Write ( const char *  name )

inlineprotectedvirtual

Write the function to the current TDirectory.

Reimplemented in ResponseFit, and ResolutionFit.

    {
        if (good()) // successful fit
            f->SetTitle(Form("%.1f", *chi2ndf));
        else {
            f->SetLineStyle(kDashed);
            f->SetTitle("fail");
        }
 
        f->SetParameters(p);
        f->SetParErrors (e);
        f->SetRange(interval.first, interval.second);
        f->Write(name);
    }

Member Data Documentation

chi2ndf

std::optional<double> chi2ndf

chi2ndfErr

std::optional<double> chi2ndfErr

best chi2/ndf

cout

std::ostream& cout

output stream, can be overwritten to reduce I/O

e

double * e

uncertainties on best parameter estimates

f

std::unique_ptr<TF1> f

Starting by passing Gaussian range.

h

const std::unique_ptr<TH1>& h

histogram ready to be fitted

interval

std::pair<float, float> interval

best fit range

p

double* p

best parameter estimation

status

std::uint32_t status

a bit-field to be used in daughter classes

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The documentation for this struct was generated from the following file:

• /builds/cms-analysis/general/DasAnalysisSystem/Core/Installer/Core/JEC/bin/fit.h