.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "tutorials/details/theta_square_plot.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_tutorials_details_theta_square_plot.py>`
        to download the full example code. or to run this example in your browser via Binder

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_tutorials_details_theta_square_plot.py:


Make a theta-square plot
========================

This tutorial explains how to make such a plot, that is the distribution
of event counts as a function of the squared angular distance, to a test
position.

.. GENERATED FROM PYTHON SOURCE LINES 13-16

Setup
-----


.. GENERATED FROM PYTHON SOURCE LINES 16-27

.. code-block:: Python


    # %matplotlib inline
    import matplotlib.pyplot as plt
    from astropy.coordinates import SkyCoord
    from astropy import units as u
    from gammapy.data import DataStore
    from gammapy.maps import MapAxis
    from gammapy.makers.utils import make_theta_squared_table
    from gammapy.visualization import plot_theta_squared_table









.. GENERATED FROM PYTHON SOURCE LINES 28-33

Get some data
-------------

Some data taken on the Crab by H.E.S.S. are used.


.. GENERATED FROM PYTHON SOURCE LINES 33-38

.. code-block:: Python


    data_store = DataStore.from_dir("$GAMMAPY_DATA/hess-dl3-dr1")
    observations = data_store.get_observations([23523, 23526])









.. GENERATED FROM PYTHON SOURCE LINES 39-44

Define a test position
-----------------------

Here we define the position of Crab


.. GENERATED FROM PYTHON SOURCE LINES 44-49

.. code-block:: Python


    position = SkyCoord(83.6324, 22.0174, unit="deg")
    print(position)






.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    <SkyCoord (ICRS): (ra, dec) in deg
        (83.6324, 22.0174)>




.. GENERATED FROM PYTHON SOURCE LINES 50-53

Creation of the theta2 plot
---------------------------


.. GENERATED FROM PYTHON SOURCE LINES 53-66

.. code-block:: Python


    theta2_axis = MapAxis.from_bounds(0, 0.2, nbin=20, interp="lin", unit="deg2")
    theta2_table = make_theta_squared_table(
        observations=observations,
        position=position,
        theta_squared_axis=theta2_axis,
    )

    plt.figure(figsize=(10, 5))
    plot_theta_squared_table(theta2_table)
    plt.show()





.. image-sg:: /tutorials/details/images/sphx_glr_theta_square_plot_001.png
   :alt: theta square plot
   :srcset: /tutorials/details/images/sphx_glr_theta_square_plot_001.png
   :class: sphx-glr-single-img





.. GENERATED FROM PYTHON SOURCE LINES 67-73

Making a theta2 plot for a given energy range
---------------------------------------------

with the function `~gammapy.makers.utils.make_theta_squared_table`, one can
also select a fixed energy range.


.. GENERATED FROM PYTHON SOURCE LINES 73-85

.. code-block:: Python


    theta2_table_en = make_theta_squared_table(
        observations=observations,
        position=position,
        theta_squared_axis=theta2_axis,
        energy_edges=[1.2, 11] * u.TeV,
    )
    plt.figure(figsize=(10, 5))
    plot_theta_squared_table(theta2_table_en)
    plt.show()





.. image-sg:: /tutorials/details/images/sphx_glr_theta_square_plot_002.png
   :alt: theta square plot
   :srcset: /tutorials/details/images/sphx_glr_theta_square_plot_002.png
   :class: sphx-glr-single-img





.. GENERATED FROM PYTHON SOURCE LINES 86-99

Statistical significance of a detection
---------------------------------------

To get the significance of a signal, the usual method consists of using the reflected background method
(see the maker tutorial: :doc:`/user-guide/makers/reflected`) to compute the WStat statistics
(see :ref:`wstat`, :doc:`/user-guide/stats/fit_statistics`). This is the well-known method of [LiMa1983]_
using ON and OFF regions.

The following tutorials show how to get an excess significance:

-  :doc:`/tutorials/analysis-1d/spectral_analysis`
-  :doc:`/tutorials/analysis-1d/extended_source_spectral_analysis`



.. _sphx_glr_download_tutorials_details_theta_square_plot.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: binder-badge

      .. image:: images/binder_badge_logo.svg
        :target: https://mybinder.org/v2/gh/gammapy/gammapy-webpage/v2.0?urlpath=lab/tree/notebooks/2.0/tutorials/details/theta_square_plot.ipynb
        :alt: Launch binder
        :width: 150 px

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: theta_square_plot.ipynb <theta_square_plot.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: theta_square_plot.py <theta_square_plot.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: theta_square_plot.zip <theta_square_plot.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_