docs: def plot_signal_power_colorplot(ax, params, fname, transient=200, Df=None,
                                  mlab=True, NFFT=1000,
                                  window=plt.mlab.window_hanning,
                                  noverlap=0,
                                  cmap = plt.cm.get_cmap('jet', 21),
                                  vmin=None,
                                  vmax=None):
      '''
      on axes plot the LFP power spectral density  
      The whole signal duration is used.
      args:
      ::
          ax : matplotlib.axes.AxesSubplot object
          fancy : bool, 
      '''
    
      zvec = np.r_[params.electrodeParams['z']]
      zvec = np.r_[zvec, zvec[-1] + np.diff(zvec)[-1]]
      
      #labels
      yticklabels=[]
      yticks = []
  
      for i, kk in enumerate(params.electrodeParams['z']):
          yticklabels.append('ch. %i' % (i+1))
          yticks.append(kk)
  
      
      freqs, PSD = calc_signal_power(params, fname=fname, transient=transient,Df=Df,
                                     mlab=mlab, NFFT=NFFT,
                                     window=window, noverlap=noverlap)
  
      #plot only above 1 Hz
      inds = freqs >= 1  # frequencies greater than 4 Hz  
      im = ax.pcolormesh(freqs[inds], zvec+50, PSD[:, inds],
                         rasterized=True, norm=LogNorm(),
                         vmin=vmin,vmax=vmax,
                         cmap=cmap, )
      
      ax.yaxis.set_ticks(yticks)
      ax.yaxis.set_ticklabels(yticklabels)
      ax.semilogx()
      ax.xaxis.set_ticks_position('bottom')
      ax.yaxis.set_ticks_position('left')
      ax.set_xlabel(r'$f$ (Hz)', labelpad=0.1)
      ax.axis(ax.axis('tight'))
  
  
      return im