add doc

matlab/tfgm/utils/plot_spectrogram.m

 function plot_spectrogram(x, dgt_params, signal_params, dgt, dynrange, clim)
 %% plot_spectrogram(x, dgt_params, signal_params, dgt, dynrange, clim)
-% Function that displays the spectrogram of a signal
-%
+% Plot spectrogram of a signal
 %  Inputs:
-%     - x: signal
-%     - dgt_params: dgt parameters
+%     - x (nd array): signal
+%     - dgt_params (struct): dgt parameters (see tf_tools/generate_dgt_parameters.m)
 %     - signal_params: signal parameters
-%     - dgt :  Gabor transform  operator
-%     - dynrange : optional
-%     - clim: optional
+%     - dgt (handle) :  DGT operator (see utils/get_stft_operators.m)
+%     - dynrange (float) : Dynamic range to be displayed.
+%     - clim (sequence): Min and max values for the colorbar. 
+%                    If both 'clim' and 'dynrange' are specified, 
+%                    then clim takes precedence.
+%
 %
 % Author : A. Marina KREME
 %%
@@ -24,8 +26,6 @@ if nargin==4
     clim = [c_max - dynrange, c_max];
 end
 
-
-
 plotdgtreal(x, dgt_params.hop, dgt_params.nbins, signal_params.fs,...,
     'dynrange', dynrange,'clim',clim)
 end