PRO dustem_write_ionfrac,file,st,help=help

;+
; NAME:
;   dustem_write_ionfrac
;
; PURPOSE:
;   writes information relating to the ionization fraction to the .DAT file
;
; CATEGORY:
;    DustEMWrap, Distributed, LowLevel, Initialization
;
; CALLING SEQUENCE:
;   dustem_write_tls,dir,st
;
; INPUTS:
;    st   : dustem data structure
;    file  : output file to be written
;
; OPTIONAL INPUT PARAMETERS:
;    None
;
; OUTPUTS:
;    None
;
; OPTIONAL OUTPUT PARAMETERS:
;    None
;
; ACCEPTED KEY-WORDS:
;    help     : writes this help
;
; COMMON BLOCKS:
;    None
;
; SIDE EFFECTS:
;    Files are written
;
; RESTRICTIONS:
;    The DustEM fortran code must be installed
;    The DustEMWrap IDL code must be installed
;
; PROCEDURES AND SUBROUTINES USED:  
;
; EXAMPLES:
;
; MODIFICATION HISTORY:
;    Evolution details on the DustEMWrap gitlab.
;    See http://dustemwrap.irap.omp.eu/ for FAQ and help.  
;-
  
  IF keyword_set(help) THEN BEGIN
     doc_library,'dustem_write_ionfrac'
     goto,the_end
  ENDIF
  
  
OPENW,unit,file,/get_lun

Ntypes=n_elements(st)
frmt="(3E15.5)"

FOR i=0L,Ntypes-1 DO BEGIN
  printf,unit,st(i).frac_cat,st(i).frac_neu,st(i).frac_ani,format=frmt
ENDFOR

close,unit
free_lun,unit

the_end:
END