Clockwise about what center point?
And what decides the starting coordinate?
If you want to sort 2D coordinates by their polar angle relative to (0,0) in the clockwise direction, convert the Cartesian coordinates to polar coordinates, wrap the radian angle values to [0:2*pi], then sort the results in descending order for the clockwise direction. The first value will be the coordinate closest to 2*pi radians.
data = [-1 -1; 4 2; -1 4]
figure()
plot(data(:,1), data(:,2), 'o')
text(data(:,1)+0.2,data(:,2),{'x','y','z'})
axis equal
axis padded
grid on
% Convert to polar coordinates
rad = cart2pol(data(:,1), data(:,2));
radWrapped = mod(rad,2*pi);
radWrapped(radWrapped==0 & rad>0) = 2*pi;
[~, sortIdx] = sort(radWrapped, 'descend');
text(data(:,1)-0.2, data(:,2),compose('%d',sortIdx),'HorizontalAlignment', 'right')
