anchor.diff:     sub_name = 'define_rad_from_geom'
       call enter_exit(sub_name,1)
       !define list of elements you are going to operate on
  -    if(present(GROUP_TYPE))then
  +    if(present(group_type_in))then
  +      group_type = group_type_in
       else!default to all
  -      GROUP_TYPE='all'
  +      group_type='all'
       endif
  -    if(GROUP_TYPE.eq.'all')then
  +    if(group_type.eq.'all')then
          ne_min=1
          ne_max=num_elems
  -    elseif(GROUP_TYPE.eq.'efield')then
  +    elseif(group_type.eq.'efield')then
   
       endif
  +
       !Define start element
       if(START_FROM.eq.'inlet')then
         inlet_count=0
  
positive.code: !##################################################################################
  !
  !*define_rad_from_geom:* Defines vessel or airway radius based on their geometric structure
    subroutine define_rad_from_geom(ORDER_SYSTEM,CONTROL_PARAM,START_FROM,START_RAD,GROUP_TYPE,GROUP_OPTIONS)
    !DEC$ ATTRIBUTES DLLEXPORT,ALIAS:"DLL_DEFINE_RAD_FROM_GEOM" :: DEFINE_RAD_FROM_GEOM
      use arrays,only: dp,num_elems,elem_field,elem_ordrs,maxgen,elem_cnct
      use indices
      use diagnostics, only: enter_exit
      implicit none
     character(LEN=100), intent(in) :: ORDER_SYSTEM,START_FROM
     character(LEN=100), optional :: GROUP_TYPE,GROUP_OPTIONS
     real(dp), intent(in) :: CONTROL_PARAM,START_RAD
     !Input options ORDER_SYSTEM=STRAHLER (CONTROL_PARAM=RDS), HORSFIELD (CONTROL_PARAM=RDH)
  
     !Local variables
     integer :: ne_min,ne_max,nindex,ne,n_max_ord,n,ne_start,&
        inlet_count
     real(dp) :: radius
  
negative.code: 
      sub_name = 'define_rad_from_file'
      call enter_exit(sub_name,1)
      if(present(radius_type_in))then
        radius_type = radius_type_in
      else
        radius_type = 'no_taper'
      endif
  
  !!! note that 'constrict' should not be used here (so is set to 1.0).
  