Filters
=======

*Filters* allows you to select a subset of the original dataset.

How to use filters
------------------

Here is the list of possible options (with their associated description) that can be provided after ``[[filters]]`` in a configuration file:

* ``region`` : To consider only the region defined by a name, see below for more information. Ex : ``east_greenland_sea``
* ``polygon`` : To consider only the region inside the polygon defined by a list of points. Ex : ``[0,80], [60, 80], [60, 85], [0, 85]``
* ``start`` : To consider only the dates from a given date (start of the month). The date must be in the following format YYYY-MM. Ex: 2019-02
* ``end`` : To consider only the dates up to a given date (end of the month). The date must be in the following format YYYY-MM. Ex: 2019-04

Set of polar ocean region masks
-------------------------------

EASE2 regional masks, provided by NSIDC. `source <https://nsidc.org/data/nsidc-0780/versions/1>`_ - `documentation <https://nsidc.org/sites/default/files/documents/technical-reference/nsidc-special-report-25.pdf>`_


.. figure:: _static/arctic_masks.png
   :scale: 55 %
   :alt: Arctic masks

.. figure:: _static/antarctic_masks.png
   :scale: 55 %
   :alt: Antarctic masks

Example
-------

Example of configuration with and without using this *filters*::

    [filters]
        polygon = [0,80], [60, 80], [60, 85], [0, 85]
        start = 2019-02
        end = 2019-04

.. figure:: _static/MAP_DIFFERENCE.png
   :scale: 33 %
   :alt: example map without filters applied

.. figure:: _static/MAP_DIFFERENCE_filters.png
   :scale: 33 %
   :alt: example map with filters applied