docs: def plotpsd(data, dt, ndivide=1, window=hanning, overlap_half=False, ax=None, **kwargs):
      """Plot PSD (Power Spectral Density).
  
      Args:
          data (np.ndarray): Input data.
          dt (float): Time between each data.
          ndivide (int): Do averaging (split data into ndivide, get psd of each, and average them).
          overlap_half (bool): Split data to half-overlapped regions.
          ax (matplotlib.axes): Axis the figure is plotted on.
          kwargs (optional): Plot options passed to ax.plot().
      """
      if ax is None:
          ax = plt.gca()
      vk, psddata = psd(data, dt, ndivide, window, overlap_half)
      ax.loglog(vk, psddata, **kwargs)
      ax.set_xlabel('Frequency [Hz]')
      ax.set_ylabel('PSD')
      ax.legend()