using conofinf to plot the cone of influence in a imagesc(time, freq, coeffs)

Hello there

I have done the cwt of a signal

coeffs=cwt(signal, scales, wavelet)

scales are obtained as this: freq=1:1: 1000 Hz

then I do the freq2scale conversion (my own routine very obvious)

scales=centfrq(wavename)./(freq*(1/fs));

so I end up having a vector of scales not equaly spaced (1/x rule)

However I want the plot to be related to the freq in Hz, so:

 imagesc(time, freq, abs(coeffs)) ---works fine!!

Now I would want to put in this plot the limits of the influence cone by doing

[PLmin,PRmax] = conofinf(wavename,scales,length(x),[]);

just doing [cone] = conofinf(wavename,scales,length(x),[]); will not work because my imagesc is ploted with time versus pseudo-frquencies.

Note that scales is a non-linear vector

How do I go about putting a cone of influence in the above imagesc plot?

many regards´ para

[Maria]

Hi, I don't know if it's still useful. But here's what I did when I had the same problem:

LenSig = length(signal);
wname = 'morl'
% construct your freq. vector
freq=1:1:1000;
% transform to scales
Fc = centfrq(wname);
scales = Fc./(f*dt);
% get wavelet transform
coefs = cwt(sig,scales,wname);
S = abs(coefs.*conj(coefs));
WT = S./N;

% plot wavelet transform / scalogram
figure;
imagesc(t,freq,WT);
axis square;
colorbar;

% annotate axes and title
title('Coefficients of continuous wavelet transform');
xlabel('Time'); 
ylabel('Pseudo-frequency');

% get cone of influence
% Here, you have to specify points at which you want to calculate COI
% as the last parameter:
cone = conofinf(wname,scales,LenSig,[1 LenSig]);
% combine left and right edges
cone = [cone{1}(:,floor(1:LenSig/2)) cone{2}(:,ceil(LenSig/2):end)];
% previous steps give you an area under COI
% you can see it with: figure; imagesc(cone);
% now, we want to get the border of this area
coi  = zeros(1,LenSig);
for idx = 1:LenSig
    valcoi = find(cone(:,idx)==1,1,'last');
    if ~isempty(valcoi)
        coi(idx) = f(valcoi);
    end
end
% now plot COI border on top of your wavelet transform
hold on;
plot(t,coi,'k','LineWidth',1.5);
hold off;

Optionally, you can hatch the area under COI, but it's a bit of a hack and it's not ideal. For this you will need hatchfill function. Once you have this function on your path, you can use it like this:

[~,h] = contourf(t,freq,cone*max(WT(:)),[1 1]*max(WT(:)));
hPatch = findobj(h, 'Type', 'patch');
hh = hatchfill(hPatch, 'cross', 45, 10);

I also constructed frequency vector and computed scales from it. This method worked fine for me.

[chin-leong wooi]

May i ask what is the variable of t and N? and what are the function f(valcoi)?

[Paramonte]

Sorry for only replying now, and for your reply: I will try that code in the next few days and will come back. Cheers

[Safura Sobri]

What is the variable for N?

Answer 1

[Paramonte]

Anybody please?