GammaLib

def classic():

    """

    """

    # Set regions

    on  = GRegions()

    off = GRegions()

    on.append(GRegionCircle(83.0, 22.0, 1.0))

    off.append(GRegionCircle(89.0, 25.0, 2.0))

    # Define energy binning

    ebds = GEbounds(10, GEnergy(0.1, "TeV"), GEnergy(100.0, "TeV"))

    # Load observation container

    obs = GObservations("obs.xml")

    # Build spectra (container that creates one spectrum per observation)

    #spec_on  = GSpectra(obs, on,  ebds)

    #spec_off = GSpectra(obs, off, ebds)

    # Derive spectrum (will create a node function internally)

    #function = GOnOffFitter(spec_on, spec_off)

    function = GCTAOnOffFitter(obs, ebds, on, off)

    function.alpha(3.7)

    function.alpha_geometric()

    opt      = GOptimizerLM()

    function.optimize(opt)

    # Build spectral model

    models = GModelsSpectrum()

    models.append(GModelSpectrumPlaw(...))

    # Derive model parameters

    function = GCTAOnOffFitter(obs, ebds, on, off, models)

    #function = GOnOffFitter(spec_on, spec_off, models)

    opt      = GOptimizerLM()

    function.optimize(opt)

######################

class GCTAOnOffFitter {

public:

    GCTAOnOffFitter(const GObservations& obs, const GEbounds& ebds,

                    const GRegions& on, const GRegions& off)

    GCTAOnOffFitter(const GObservations& obs, const GEbounds& ebds,

                    const GRegions& on, const GRegions& off, const GModels& models)

protected:

    GEbounds                  m_ebds;

    GRegions                  m_reg_on;

    GRegions                  m_reg_off;

    std::vector<GSpectrum>    m_spec_on;

    std::vector<GSpectrum>    m_spec_off;

    std::vector<GCTAResponse> m_rsp;

};