Filtering data
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A simpler version of PROCAR file containing only a subset of information from the original dataset can be generated with this utility.  This feature is very useful when there are many bands in the PROCAR file (e.g. in heterostructures or supercells calculations) making the file size enormously large for post-processing while only bands near the Fermi-level are needed for analysis. In this case, one can filter data of selected bands near the Fermi-level. This considerably reduces the file size and makes the post-processing of data faster. In the same way, one could use the ``filter`` utility to filter the **PROCAR** file to extract information regarding particular spins, atoms, or orbitals in a relatively smaller **PROCAR-new** file.

The following example extracts information of bands ranging from index 50 to 70 from a **PROCAR** file (Fermi-level is near band \#60) while ignoring all other bands located far from the Fermi-level, and stores resulting dataset in a new file named **PROCAR-band50-70**. Now the new **PROCAR-band50-70** file can be used for further post-processing of data at relatively low memory requirements::

	pyprocar.filter('PROCAR','PROCAR-band50-70',bands=[50,70])

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To filter selected orbitals 
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To make a new PROCAR file containing only three columns, one for :math:`s` orbitals, one for :math:`p`, and one for total (real total, not total of :math:`s+p`)::

	pyprocar.filter('PROCAR’,'PROCAR-filtered_sp’, orbitals=[[0],[1,2,3]])

If you want to select only :math:`p_x` orbitals, just use ``orbitals=[[3]]``.

In the same way to plot the projection of total :math:`p`-orbitals use ``orbitals=[[1,2,3]]``  (i.e. :math:`px+py+pz`). Same goes for other orbitals. 

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To filter selected atoms 
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Usage::

	pyprocar.filter(‘PROCAR’,’PROCAR-filter_ATOMS’, atoms=[[0]])

PyProcar counts each row of ions in PROCAR file starting from 0. Keep in mind: ``atoms=0`` does not define the atom_type, rather it defines only the first ion in the POSCAR. So if you have more than one ion of the same element, use ``atoms = [[0,1,2,3,...]]``.