.. include:: ../references.txt .. _spectrum: ******************************* spectrum - 1D spectrum analysis ******************************* .. currentmodule:: gammapy.spectrum Introduction ============ `gammapy.spectrum` holds functions and classes related to 1D region based spectral analysis. This includes also simulation tools. The basic of 1D spectral analysis are explained in `this `__ talk. A good reference for the forward-folding on-off likelihood fitting methods is Section 7.5 "Spectra and Light Curves" in [Naurois2012]_, in publications usually the reference [Piron2001]_ is used. A standard reference for the unfolding method is [Albert2007]_. Getting Started =============== The following code snippet demonstrates how to load an observation stored in OGIP format and fit a spectral model. .. code-block:: python from gammapy.spectrum import SpectrumDatasetOnOff from gammapy.utils.fitting import Fit from gammapy.spectrum.models import PowerLaw filename = '$GAMMAPY_DATA/joint-crab/spectra/hess/pha_obs23523.fits' dataset = SpectrumDatasetOnOff.from_ogip_files(filename) model = PowerLaw( index=2, amplitude='1e-12 cm-2 s-1 TeV-1', reference='1 TeV', ) dataset.model = model fit = Fit([dataset]) result = fit.run() model.parameters.covariance = result.parameters.covariance print(model) It will print the following output to the console: .. code-block:: text PowerLaw Parameters: name value error unit min max frozen --------- --------- --------- -------------- --- --- ------ index 2.817e+00 1.496e-01 nan nan False amplitude 5.142e-11 6.423e-12 cm-2 s-1 TeV-1 nan nan False reference 1.000e+00 0.000e+00 TeV nan nan True Covariance: name index amplitude reference --------- --------- --------- --------- index 2.239e-02 6.160e-13 0.000e+00 amplitude 6.160e-13 4.126e-23 0.000e+00 reference 0.000e+00 0.000e+00 0.000e+00 Using `gammapy.spectrum` ======================== For more advanced use cases please go to the tutorial notebooks: * :gp-notebook:`spectrum_simulation` - simulate and fit 1D spectra using pre-defined or a user-defined model. * :gp-notebook:`spectrum_analysis` - spectral analysis starting from event lists and field-of-view IRFs. The following pages describe ``gammapy.spectrum`` in more detail: .. toctree:: :maxdepth: 1 fitting Reference/API ============= .. automodapi:: gammapy.spectrum :no-inheritance-diagram: :include-all-objects: .. automodapi:: gammapy.spectrum.models :no-inheritance-diagram: :include-all-objects: