Determine indices of how many times (x,y) coordinates occur in 2d vector

I wand to check if 2d coordinates of type (x,y) occur many times in 2d vector. I just want to count the number of times they occur if they occur at least two times and I also need the indices for this secondt (and beyond) times they occur.

Answer 1

[Star Strider]

Try this:

M = randi(5, 25, 2);                                                                                    % Create ‘LatLon’ Data
[Mu,~,idx] = unique(M, 'rows');                                                                         % Unique Rows
Tally = accumarray(idx, (1:numel(idx)).', [], @(x) {M(x,:)});                                           % Calculate Frequencies, Return Pairs By Group
pairs = cellfun(@(x)size(x,1), Tally);                                                                  % Recover ‘LatLon’ Pairs
idxc = accumarray(idx, (1:numel(idx)).', [], @(x) {x.'});                                               % Get Indices
idxmtx = zeros(numel(pairs),max(pairs(:)));                                                             % Create Matrix For Indices
for k = 1:size(idxmtx,1)
    idxmtx(k,1:pairs(k)) = [idxc{k}];                                                                   % Assign Indices To Appropriate Rows
end
[~,ixs] = sort(pairs, 'descend');                                                                       % Sort Them
Result = table(Mu(ixs,:),pairs(ixs),idxmtx(ixs,:), 'VariableNames',{'LatLon','Frequency','Indices'});   % Output Table Of Pairs & Frequencies
ResultSel = Result(pairs(ixs) > 1,:)                                                                    % Select Only Occurrences > 1

Substitute your coordinates for the ‘M’ matrix in my code.

If the coordinates are not exact, consider substituting uniquetol with the ByRows name-value pair for unique.

.

Answer 2

[Ramya Dodla]

MATLAB ismember function will provide you with the indices of (x,y) occurance. Try the following code. This will give you a 5x1 array where 1 represent (x,y) occurance.

    x = 0;
    y = 1;
    arr=[2 0 0 0 0; 1 1 1 1 1];
    presentMatrix = ismember(arr.', [x y], 'rows');
    

The following code should provide number of occurances

    sum(presentMatrix(:) == 1)