= PDAFomi_diag_nobstypes = 

This page documents the routine `PDAFomi_diag_nobstypes` 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 the number of observation types that are active in an assimilation run. 

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_nobstypes(nobstypes)

    INTEGER, INTENT(inout) :: nobstypes   ! Number of observation types
}}}

**Note:**
 * `nobstypes` is commonly used as the upper limit of a loop running over all observation types. In this way `nobstypes` can be used with the PDAFomi_diag routines that return different observation-related arrays for a single observation type.