= PDAF_local_weight = 


This page documents the routine `PDAF_local_weight` of PDAF. 

The routine is used for localization in the analysis step of a filter and computes a weight according to the specified distance and the settings for the localizing function.

The interface is the following:
{{{
  SUBROUTINE PDAF_local_weight(wtype, rtype, cradius, sradius, distance, &
     nrows, ncols, A, var_obs, weight, verbose)
}}}
with the following arguments:
 * `wtype` : `integer, intent(in)`[[BR]] Type of weight function:[[BR]] (0) unit weight (=1 up to radius `cradius`) [[BR]] (1) exponential decrease (1/e at distance=sradius; 0 for distance>cradius)[[BR]] (2) 5th order polynomial with support radius sradius (Gaspari&Cohn 1999; 0 for distance>sradius)
 * `rtype` : `integer, intent(in)`[[BR]] Type of regulated weighting:[[BR]] (0) no regulation[[BR]] (1) regulation using mean variances[[BR]] (2) regulation using variance of single observation point
 * `cradius` : `real, intent(in)`[[BR]] Cut-off radius (weight is always =0 for distance>cradius)
 * `sradius` : `real, intent(in)`[[BR]] Support radius
 * `distance` : `real, intent(in)`[[BR]] Distance to observation
 * `nrows` : `integer, intent(in)`[[BR]] Number of rows in matrix A
 * `ncols` : `integer, intent(in)`[[BR]] Number of columns in matrix A
 * `A` : `real, intent(in), dimension(nrows,ncols)`[[BR]] Input matrix (only used for regulated localization)
 * `var_obs` : `real, intent(in)`[[BR]] Observation variance (only used for regulated localization)
 * `weight` : `real, intent(out)`[[BR]] computed localization weight
 * `verbose` : `integer, intent(in)`[[BR]] Verbosity flag