Try comparing the y coordinates at a given time stamp to the values present in the coherence matrix and coi vector.
Pseudocode of the same can be like:
% Wavelet coherence and cross-spectrum
[wcoh, wcs, period, coi] = wcoherence(x, y);
% Get the size of the coherence matrix
[rows, cols] = size(wcoh)
% Identify data points outside the cone of influence
coi_indices = zeros(rows, cols);
for i = 1:rows
for j = 1:cols
if wcoh(i,j) < coi(j)
coi_indices(i, j) = 1; % Data point outside the COI (mark that index)
end
end
end
