find barycenter of several objects on an image

% take the upper part of the matrix (above the diagonal)
crossing_tri=tril(nan(size(crossing_table)))+[tril(crossing_table')]';
% remove the diagonal (with the cloud around it)
for icol=2:size(crossing_tri,2)
     lastblack=find(crossing_tri(1:icol,icol)==0,1,'last');
     crossing_tri(lastblack:icol,icol)=0;
end
% make it a logical matrix (with no NaN)
ab(isnan(crossing_tri))=0;
figure
imshow(crossing_tri)
hold on
s=regionprops(logical(crossing_tri),'Centroid')
centroids=cat(1,s.Centroid)
plot(centroids(:,1),centroids(:,2),'rx')