= PDAFomi_diag_nobs = 

This page documents the routine `PDAFomi_diag_nobs` of PDAF, which was introduced with PDAF V3.0. This is part of the 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 the following: 
{{{
  SUBROUTINE PDAFomi_diag_nobs(nobstypes)
}}}
with the following argument:
{{{
    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