how to display spectrogram of a audio in App Designer

I want show the figure in the app designer interface.But did not success.I only can plot it outside of app designer.I am using Matlab 2018b.

spectrogram(audio,window,noverlap,nfft,fs,'yaxis');

Anyone know how to do it. Thanks.

Answer 1

[Edgar Guevara]

Dear Austin,

You need to specify which axes will be used for plotting, inside a callback for plotting such spectrogram, you may use the following example code:

t = 0:0.001:2;
x = chirp(t,100,1,200,'quadratic');
myAxe = app.UIAxes;
[S,F,T] = spectrogram(x,128,120,128,1e3);
imagesc(myAxe, T, F, log(1+abs(S)) ); %plot the log spectrum
set(myAxe,'YDir', 'normal'); % flip the Y Axis so lower frequencies are at the bottom

Let me know if that solves your problem.

[austin austin]

Thank you so much.

[austin austin]

By the way, the way you did, it is work good. But the spectrogram color is a little darker. Is there any way can make it brighter? Thank you.

[Edgar Guevara]

I think your spectrogram is not displayed on log scale, try the following code, which reproduces the output from the built-in function:

    methods (Access = private)

        % Button pushed function: Button
        function plotSpec(app, event)
            t = 0:0.001:2;
            x = chirp(t,100,1,200,'quadratic');
            myAxe = app.UIAxes;
            [S,F,T] = spectrogram(x,128,120,128,1e3);
            imagesc(myAxe, F, T, log(abs(S'))); %plot the log spectrum
            set(myAxe,'YDir', 'normal'); % flip the Y Axis so lower frequencies are at the bottom 
            axis square 
            axis tight
            colorbar
        end
    end

As you can see: