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

.. only:: html

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

        :ref:`Go to the end <sphx_glr_download_gallery_tutorials_measure_noise.py>`
        to download the full example code.

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

.. _sphx_glr_gallery_tutorials_measure_noise.py:


.. _tutorial_measure_noise:

Measure noise of a FITS file
############################

Beginner's tutorial showing how to measure the noise of a
`~madcubapy.io.MadcubaMap` object. For a detailed overview go to the
:ref:`documentation page<measure_noise>`.

First we read the FITS file as a MadcubaMap object.

.. GENERATED FROM PYTHON SOURCE LINES 14-22

.. code-block:: Python



    from madcubapy.io import MadcubaMap

    # Read fits file
    madcuba_map = MadcubaMap.read(
        "../examples/data/IRAS16293_SO_2-1_moment0_madcuba.fits")








.. GENERATED FROM PYTHON SOURCE LINES 30-81

To measure the noise level of the map we have two options:

* We can use the :func:`~madcubapy.operations.maps.measure_noise` function on
  the `~madcubapy.io.MadcubaMap` object to obtain the sigma value in a
  variable (this also works for `~astropy.nddata.CCDData` objects):

  .. code-block:: python

      sigma = measure_noise(madcuba_map)

* Or we can use the
  :meth:`MadcubaMap.update_sigma() <madcubapy.io.MadcubaMap.update_sigma>`
  method to automatically store the measured sigma value in the FITS header,
  on the ``SIGMA`` card, and have it available for future analysis:

  .. code-block:: python

      madcuba_map.update_sigma()

  .. note::

      Remember that changes applied to a `~madcubapy.io.MadcubaMap` object
      during a python run are not stored into the FITS file until the file is
      explicitly saved:

      .. code-block:: python

          madcuba_map.write("output_file.fits", overwrite=True)

How it works
------------

Both options behave in the same way. A window will appear where the user can
select polygons using the mouse:

- Left clicks create polygon vertices.
- Right click closes the current polygon, and a subsequent left click
  starts a new polygon.

This window also offers buttons to change the statistic used to calculate
the noise.

Once we have the desired polygons, we can press the **Finish** button to
close the window and return the noise value in a variable (the case of
:func:`~madcubapy.operations.maps.measure_noise`) or stored in the FITS
header (the case of
:meth:`MadcubaMap.update_sigma() <madcubapy.io.MadcubaMap.update_sigma>`).

.. figure:: ../_static/figures/measure_noise.png
    :alt: Image with pcolor
    :figclass: align-center


.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 0.015 seconds)


.. _sphx_glr_download_gallery_tutorials_measure_noise.py:

.. only:: html

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

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

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

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

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

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

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


.. only:: html

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

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