MATLAB: How to generate a scrolling spectrogram using the SURF command in MATLAB 7.5 (R2007b)

MATLAB

I would like to create a spectogram that is displayed in stages as it is being computed.

Best Answer

This may be done by limiting the view of original plot during the plotting process.
Use the following code to implement this.
%%How can I have my spectrogram scroll on display using the SURF command?
% 
% This can be done by calling the SURF command with new updates either in a
% for loop or through a timer triggered calling function to update the
% plot. In this example in the final figure (3) the figure is updated in a
% simple for loop.
%%Direct visualization of Spectrogram using the SPECTROGRAM function
T = 0:0.001:1;
X = chirp(T,100,1,200,'q');
spectrogram(X,128,120,128,1E3); 
title('Quadratic Chirp');
%%Using the SURF command instead of the default SPECTROGRAM Plot
T = 0:0.001:1;
X = chirp(T,100,1,200,'q');
[Y,F,T,P] = spectrogram(X,128,120,128,1E3);
figure
h = surf(F,T,10*log10(abs(P')),'EdgeColor','none');
axis xy; axis tight; colormap(jet); view(0,20);
xlabel('Time');
ylabel('Frequency (Hz)');
%%Allowing data to scroll using the SURF command
T = 0:0.001:1;
X = chirp(T,100,1,200,'q');
[Y,F,T,P] = spectrogram(X,128,120,128,1E3);
[Prows,Pcols] = size(P);
figure
P_temp = zeros(Prows,Pcols);
% Fix Axis Limits for Plotting so the scrolling appears to be constant
xmin = 0;
xmax = 1;
ymin = -120;
ymax = 120;
for i = 1:Prows
      % Create new matrices (T,F,P) so that they can be used by SURF
      P_temp(1:i,:) = P(1:i,:);
      % Surf Plot the Matrices which update in a for loop
      h = surf(F,T,10*log10(abs(P_temp')),'EdgeColor','none');
      axis xy; axis tight; colormap(jet); view(0,20);
      % Set the axis limits so they appear constant during the plotting
      % process
%    xlim([xmin xmax])
      ylim([ymin ymax])
      xlabel('Time');
      ylabel('Frequency (Hz)');
      pause(0.01)
end
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