How to do subplot using cwt()
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Shengjie Gao
on 7 Mar 2021
Edited: Jeremy Scholze
on 29 Jul 2022
Hey, I would like to plot a 3*3 subplots containing 9 figures from cwt(). However, I found it impossible to do that by simply doing
subplot(3,3,1)
cwt(data1)
subplot(3,3,2)
cwt(data2)
My guess is that we have to manually extract the cwt features and plot by ourselves under the subplot(). If yes, could anyone share a sample code for this part? If not, what should I do to draw such a subplot?
Thank you very much!
3 Comments
Walter Roberson
on 7 Mar 2021
Ah, I see what you mean. The code specifically clears the current figure before plotting.
In some cases, the code creates two axes, but I have not figured out yet which cases that corresponds to.
The code is taking the wavelet transform information (what would normally be the first output) and abs() it, and effectively does an imagesc() of that.
Accepted Answer
Monisha Nalluru
on 11 Mar 2021
Hi Shengjie,
cwt() would support subplots only with complex valued input signals that will plot the analytic and anti-analytic parts into seperate subplot.
In all other case, the output of cwt can be used with surface,pcolor or image to produce similar plot
As an example
load mtlb
figure
subplot(211)
[wt1,f1] = cwt(mtlb,'bump',Fs);
pcolor(1:numel(mtlb),log2(f1),abs(wt1));
shading interp;
subplot(212)
[wt2,f2] = cwt(mtlb,Fs);
pcolor(1:numel(mtlb),log2(f2),abs(wt2));
shading interp
Example cwt supporting subplots for complex valued iput ,
load npg2006;
plot(npg2006.cx); hold on; grid on;
xlabel('Eastward Displacement (km)');
ylabel('Northward Displacement (km)');
plot(npg2006.cx(1),'^','markersize',11,'color','r',...
'markerfacecolor',[1 0 0 ]);
figure;
cwt(npg2006.cx,npg2006.dt);
Hope this helps!
More Answers (1)
Jeremy Scholze
on 27 Jul 2022
Edited: Jeremy Scholze
on 29 Jul 2022
Option 1: My Solution
Use
[cfs, frq] = cwt(data,Fs);
tms = (0:numel(data)-1)/Fs;
to calculate the wavelet transform and then do
imagesc(tms,frq,abs(C)); c = colorbar; c.Label.String = 'Magnitude';
axis tight; shading flat;
xlabel('Time (s)')
ylabel('Frequency (Hz)')
set(gca,'yscale','log')
to generate the plot. Your axes will be screwed up and you won't have the frequency bounds area greyed out but it'll work.
Option 2: MATLAB's Solution (less efficient)
openExample('wavelet/PlotCWTScalogramInSubplotExample')
They address this issue. Just run this in your command window ^
Edit: My method is apparently WAY more efficient than using the surface command in MATLAB's solution. Would recommend imagesc before surface. surface crashed my computer. The axis controls in MATLAB's solution will still work with imagesc.
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