Plotting cone of influence in Morlet wavelet power spectrum in MATLAB - matlab

Question

I tried generating the cone of influence for a Morlet wavelet power spectrum using the following MATLAB code:
cone = conofinf('morl',1:365,LenSig,[],'plot');
However, all I get is a strange looking shaded area bounded by two linear lines. It doesn't look like a cone of influence for Morlet wavelet power spectrum.
What did I do wrong?

Answer 1

I guess you wanted to output COI at the borders of your wavelet transform. In this case you have to specify the last parameter as non-empty vector, but with coordinates, where you need COI to be computed, e.g.
cone = conofinf('morl',1:365,LenSig,[1 LenSig],'plot');
I had a similar task and here's what I did:
figure;
% plot wavelet transform / scalogram
imagesc(t,scales,WT);
axis square;
colorbar;
% annotate axes and title
title('Coefficients of continuous wavelet transform');
xlabel('Time (or space) b');
ylabel('Scales a');
% 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 (here's an example how to use it). Once you have this function on your path, you can use it like this:
[~,h] = contourf(t,scales,cone*max(WT(:)),[1 1]*max(WT(:)));
hPatch = findobj(h, 'Type', 'patch');
hh = hatchfill(hPatch, 'cross', 45, 10);