= PDAFomi_diag_get_HX = 

This page documents the routine `PDAFomi_diag_get_HX` of PDAF, which was introduced with PDAF V3.0. This is part of the [wiki:PDAFomi_observation_diagnostics PDAF-OMI observation diagnostics module]. 

The routine returns a pointer to the array of the observed ensemble for the specified observation type (`id_obs`).

Usually all PDAFomi_diag routines are called in `prepoststep_pdaf` where the observation information can be retrieved and analyzed.

The interface is: 
{{{
  SUBROUTINE PDAFomi_diag_get_HX(id_obs, dim_obs_p_diag, HX_p_ptr)

    INTEGER, INTENT(in)  :: id_obs                   ! Index of observation type to return
    INTEGER, INTENT(out) :: dim_obs_p_diag           ! Observation dimension
    REAL, POINTER, INTENT(out) :: HX_p_ptr(:,:)      ! Pointer to observed ensemble mean
}}}

**Notes:**
 * In case of a parallelized model, the array `HX_p_prt` contains the observed ensemble for the process-sub-domain
 * In Fortran user code the pointer to the observed ensemble should be declared in the form[[BR]] `REAL, POINTER :: HX_p_ptr(:,:)`[[BR]] It does not need to be allocated. The target array has the size `(dim_obs_p_diag, dim_ens)`
 * If the observation diagnostics have not be activated by using [wiki:PDAFomi_set_obs_diag] the pointer will not be set and `dim_obs_diag=0` will be returned. This value can be checked before assessing the pointer array.