How can I force the time-axis unit of spectrogram to be 'second(s)' ?

When I use the spectrogram function (https://www.mathworks.com/help/signal/ref/spectrogram.html) , I find that depends on the time duration of the y data, the time-axis units are dynamic, shifting between 'second(s)' and 'milisecond(s)'. So is it possible to force the unit to be 'second(s)'?

[Adam Danz]

Are you referring to your inputs or are you referring to something in the plot produced by spectrogram?

It would be helpful to provide a screen shot of the figure or supply the input data, depending on what you're describing.

[zhehao.nkd]

Sorry for my vague description. I am referring to the plot generated by function spectrogram without defining the output.

For example,

fs = 32000;
y1 = wgn(1*fs,1,1);
y2 = wgn(2*fs,1,1);

figure; 
subplot(2,1,1)
spectrogram(y1,hamming(512),512-round(fs/1e3),512,fs,'yaxis');
subplot(2,1,2)
spectrogram(y2,hamming(512),512-round(fs/1e3),512,fs,'yaxis');

This two subplots will have different time units as ms and s. So how can I force the unit to be s?

Answer 1

[Adam Danz]

I don't know whether there's an input to spectrogram that could solve this but here's how to fix the labels after the plots are created.

You could detect whether the x-axis is in seconds or ms by the xlabel;

if strcmpi(ax1.XLabel.String, 'Time (ms)')

ax1.XTickLabels = compose('%.1f',ax1.XTick/1000); % set tick labels

xlabel(ax1, 'Time (s)') % set axis label

end

P1=[10,-1]; 
fs = 32000;
y1 = wgn(1*fs,1,1);
y2 = wgn(2*fs,1,1);
figure; 
ax1 = subplot(2,1,1); % get handle
spectrogram(y1,hamming(512),512-round(fs/1e3),512,fs,'yaxis');
subplot(2,1,2)
spectrogram(y2,hamming(512),512-round(fs/1e3),512,fs,'yaxis');

ax1.XTickLabels = compose('%.1f',ax1.XTick/1000); % set tick labels
xlabel(ax1, 'Time (s)') % set axis label

[zhehao.nkd]

Thank you! It's a great solution.