= PDAF_localfilter = 

This page documents the function `PDAF_localfilter` of PDAF, which was introduced with PDAF 3.0.

The function is an alternative to the subroutine [wiki:PDAF_get_localfilter]. In `PDAF_localfilter` the return value of the function is directly used, while for `PDAF_get_localfilter` the return value is an argument of the routine.

The function returns the information whether the chosen filter is a domain-localized filter (LESTKF, LETKF, LSEIK, LNETF). It also indicates the ENSRF since these filters use the same observation handling of the domain-localized filters. The function can be called in `assimilate_pdaf` to control whether to call either PDAF3_assimilate_global or PDAF3_assimilate_local (or PDAF3_put_state_global or PDAF3_put_state_local).
The function can only be used if PDAF was initialized before by a call to `PDAF_init`.

The interface is:
{{{
  INTEGER FUNCTION PDAF_localfilter()
}}}
without arguments. The return value is
 * 1 for local filters (including ENSRF/EAKF),[[br]]
 * 0 for global filters (including LEnKF, which performs covariance localization)

The return value can be directly used, e.g. as
{{{
  IF (PDAF_localfilter() == 1) THEN
    CALL PDAF3_assimilate_local(...)
  ELSE
    CALL PDAF3_assimilate_global(...)
  ENDIF
}}}

**Notes:**
 * The difference between the return values 0 and 1 is mainly the way how PDAF-OMI handles observations. 
 * For the ENSRF/EAKF, PDAF_localfilter() also returns the value 1. This is because the observation handling for the ENSRF/EAKF uses the same approach as for domain-localized filters