;--------------------------------------------------------------
; input, v = an array whose missing value are set to missing
;        width = width argument to smooth
;        missing = the missing value for v
;
; output, v = the smoothed version of v
;--------------------------------------------------------------
function smooth_nan, v, width, missing
  v[where(v eq missing,/NULL)] = !Values.F_NaN
  v = smooth(v,width,/NAN)
  v[where(finite(v,/Nan),/Null)] = missing
  return, v
end