PRO dustem_write_ionfrac,file,st

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

END