How can I plot frequency vs magnitude of wavelet transform? I am running Morlet continuous wavelet transform. I have got wscalogram of signal and now I want to plot freq-magnitude like the following picture., but I don't know how to do it:

  

I've used scal2freq MATLAB function to convert scales to pseudo frequencies. Also I have some frequencies in my signal that have a large damping ratio(4%) so they are not well visible in plot. How can I exaggerate these highly damped modes?  

I am using MATLAB, here is my codes: 

% Import the text4.txt to matlab workspace. and save it under name "data"
t=linspace(0,30,301);
Fs=ceil(inv(t(2)-t(1)));
x=data(:,4); % use x=data(:,3),x=data(:,5) too. first column is time,second is refrence
wname = 'morl';
scales = 1:1:256;
coefs = cwt(x,scales,wname,'lvlabs');
freq = scal2frq(scales,wname,1/Fs);
surf(t,freq,abs(coefs));shading('interp');
axis tight; xlabel('Seconds'); ylabel('Pseudo-Frequency (Hz)');
axis([0 30 0 1 0 60])
xlabel('Time'); ylabel('Frequency');
figure;
sc=wscalogram('image',coefs,'scales',freq,'ydata',x);
hold on 


My current plot looks like this:
Continuous wavelet transform (CWT) is a method for time-scale analysis. Yes, you read it correctly, scale, not frequency. However, it is possible to map the scales to frequencies, and even quite easily. Since you are a MATLAB user, you will probably want to use this function, which does the following:


  F = scal2frq(A,'wname',DELTA) returns the pseudo-frequencies corresponding to the scales given by A, the wavelet function 'wname' (see wavefun for more information) and the sampling period DELTA.


As you can read, the frequencies are not the real frequencies in the signal, but approximations. If you want the real frequencies, you should be using the short-time Fourier transform (STFT).

So, when should one use the CWT? As a general principle, wavelets work well when the signals are transient (i.e. have quick changes).

EDIT: haha, I don't know what I'm doing here. sorry :-D completely missed the point of your question. Just read the title....