PRO sp2wr, file, x, y, header

; Write a 1d function into a spectrum format 2 file

  ndat = n_elements(x)

  openw,lun,file,/get_lun

  PrintF, lun, header
  PrintF, lun 
  PrintF, lun, ndat

  FOR i = 0L,ndat-1 DO BEGIN
    xx = x(i) & yy = y(i)
    PrintF, lun, xx,yy, format='(f10.4,2x,e12.5)'
  ENDFOR

  close,lun
  free_lun, lun

END