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let us consider following code

function [sca_1,sca_2,sca_3,sca_4]=calc_wavelet(y,wname,scales,freq,fs)
%y-input signal
%wname-wavelet basis name
%freq-test frequencies
%fs-sampling rate
TAB_Sca2Frq = scal2frq(scales,wname,1/fs);
[~,idxSca_1] = min(abs(TAB_Sca2Frq-freq(1)));
sca_1 = scales(idxSca_1);
[mini,idxSca_2] = min(abs(TAB_Sca2Frq-freq(2)));
sca_2 = scales(idxSca_2);
[~,idxSca_3] = min(abs(TAB_Sca2Frq-freq(3)));
sca_3 = scales(idxSca_3);
[mini,idxSca_4] = min(abs(TAB_Sca2Frq-freq(4)));
sca_4 = scales(idxSca_4);
coefs = cwt(y,scales,wname);
clf; wscalogram('image',coefs,'scales',scales,'ydata',y);
hold on
plot([1 size(coefs,2)],[sca_1 sca_1],'Color','m','LineWidth',2);
plot([1 size(coefs,2)],[sca_2 sca_2],'Color','m','LineWidth',2);
plot([1 size(coefs,2)],[sca_3 sca_3],'Color','m','LineWidth',2);
plot([1 size(coefs,2)],[sca_4 sca_4],'Color','m','LineWidth',2);

i have took following data

>> wname = 'morl';
scales = 1:1:128;
>> fs=100;
>> freq=[13.7   10.5    29.9    31
];

when i run following code

[scal_1,scal_2,scal_3,scal_4]=calc_wavelet(B,wname,scales,freq,fs);

got result :

enter image description here

one frequency is lost,i have tried also following basis

>> wname = 'mexh';
>> wname = 'morl';
>> wname = 'haar';
>> wname = 'gaus4';

please pay attention that my model is following

https://dsp.stackexchange.com/questions/15559/understanding-1d-wavelet-analysis

so which wavelet basis should i choose for good spectral resolution?i want to use wavelet for ability to distinguish signals which are closed spaced to each other,like in my case

freq=[13.7 10.5 29.9 31];

it could be even more closed to each other

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The window shape chosen for your wavelet basis will generally only have a slight effect on frequency resolution. To increase frequency resolution more, increase a scale factor that is related or proportional to the window length for a given frequency. This will also decrease temporal resolution.

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  • $\begingroup$ i have tried to increase scales,but it seems that wavelet also have same problem of resolution as generally windows,,is it right? $\endgroup$ – dato datuashvili Apr 12 '14 at 20:56
  • $\begingroup$ in fact when we have unknow frequency components,it always big question how big scales should i choose?as it is related to AR model :How big model order should i choose $\endgroup$ – dato datuashvili Apr 12 '14 at 20:58
  • $\begingroup$ DFT windows have more problems with resolution than wavelet scale, but the problem they have in common are similar. $\endgroup$ – hotpaw2 Apr 12 '14 at 21:00
  • $\begingroup$ especially for sinusoidal models in noise,so that means that there is not standard base or scales related to wavelet to such models? $\endgroup$ – dato datuashvili Apr 12 '14 at 21:03

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