.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "tutorials/api/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_api_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_api_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 28-31
Check setup
-----------
.. GENERATED FROM PYTHON SOURCE LINES 31-37
.. code-block:: Python
from gammapy.utils.check import check_tutorials_setup
check_tutorials_setup()
.. rst-class:: sphx-glr-script-out
.. code-block:: none
System:
python_executable : /home/runner/work/gammapy-docs/gammapy-docs/gammapy/.tox/build_docs/bin/python
python_version : 3.9.22
machine : x86_64
system : Linux
Gammapy package:
version : 2.0.dev1326+g6403c0061
path : /home/runner/work/gammapy-docs/gammapy-docs/gammapy/.tox/build_docs/lib/python3.9/site-packages/gammapy
Other packages:
numpy : 1.26.4
scipy : 1.13.1
astropy : 6.0.1
regions : 0.8
click : 8.1.8
yaml : 6.0.2
IPython : 8.18.1
jupyterlab : not installed
matplotlib : 3.9.4
pandas : not installed
healpy : 1.17.3
iminuit : 2.31.1
sherpa : 4.16.1
naima : 0.10.0
emcee : 3.1.6
corner : 2.2.3
ray : 2.46.0
Gammapy environment variables:
GAMMAPY_DATA : /home/runner/work/gammapy-docs/gammapy-docs/gammapy-datasets/dev
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Get some data
-------------
Some data taken on the Crab by H.E.S.S. are used.
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.. 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 49-52
Define a test position
-----------------------
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.. code-block:: Python
position = SkyCoord.from_name("crab")
print(position)
.. rst-class:: sphx-glr-script-out
.. code-block:: none
<SkyCoord (ICRS): (ra, dec) in deg
(83.6324, 22.0174)>
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Creation of the theta2 plot
---------------------------
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.. 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/api/images/sphx_glr_theta_square_plot_001.png
:alt: theta square plot
:srcset: /tutorials/api/images/sphx_glr_theta_square_plot_001.png
:class: sphx-glr-single-img
.. GENERATED FROM PYTHON SOURCE LINES 75-80
Making a theta2 plot for a given energy range
---------------------------------------------
with the function `make_theta_squared_table`, one can also select a fixed energy range.
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.. 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/api/images/sphx_glr_theta_square_plot_002.png
:alt: theta square plot
:srcset: /tutorials/api/images/sphx_glr_theta_square_plot_002.png
:class: sphx-glr-single-img
.. GENERATED FROM PYTHON SOURCE LINES 93-104
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 Li&Ma [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_api_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/main?urlpath=lab/tree/notebooks/dev/tutorials/api/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>`_