(sr, nfft)
return (sr / 2) / (nfft / 2)
:param: sr, sample rate
  :param: nfft, fft points
  :return: freq resolution of one point
:param: sr, sample rate
  :param: nfft, fft points
  :return: freq resolution of one point
: param : sr sample rate : param : nfft fft points : return : freq resolution of one point
def freq_resolution(sr, nfft):
  '''
  :param: sr, sample rate
  :param: nfft, fft points
  :return: freq resolution of one point
  '''
  return (sr / 2) / (nfft / 2)
def freq_resolution ( sr , nfft ) : return ( sr / 2 ) / ( nfft / 2 )