code: def _realwavelets(s_freq, freqs, dur, width):
      
      x = arange(-dur / 2, dur / 2, 1 / s_freq)
      wavelets = empty((len(freqs), len(x)))
  
      g = exp(-(pi * x ** 2) / width ** 2)
  
      for i, one_freq in enumerate(freqs):
          y = cos(2 * pi * x * one_freq)
          wavelets[i, :] = y * g
  
      return wavelets
docs: Create real wavelets, for UCSD.
  
      Parameters
      ----------
      s_freq : int
          sampling frequency
      freqs : ndarray
          vector with frequencies of interest
      dur : float
          duration of the wavelets in s
      width : float
          parameter controlling gaussian shape
  
      Returns
      -------
      ndarray
          wavelets