I am writing a program where I need to delete duplicate points stored in a matrix. The problem is that when it comes to check whether those points are in the matrix, MATLAB can't recognize them in the matrix although they exist.

In the following code, intersections function gets the intersection points:

[points(:,1), points(:,2)] = intersections(...
    obj.modifiedVGVertices(1,:), obj.modifiedVGVertices(2,:), ...
    [vertex1(1) vertex2(1)], [vertex1(2) vertex2(2)]);

The result:

>> points
points =
   12.0000   15.0000
   33.0000   24.0000
   33.0000   24.0000

>> vertex1
vertex1 =
    12
    15

>> vertex2    
vertex2 =
    33
    24

Two points (vertex1 and vertex2) should be eliminated from the result. It should be done by the below commands:

points = points((points(:,1) ~= vertex1(1)) | (points(:,2) ~= vertex1(2)), :);
points = points((points(:,1) ~= vertex2(1)) | (points(:,2) ~= vertex2(2)), :);

After doing that, we have this unexpected outcome:

>> points
points =
   33.0000   24.0000

The outcome should be an empty matrix. As you can see, the first (or second?) pair of [33.0000 24.0000] has been eliminated, but not the second one.

Then I checked these two expressions:

>> points(1) ~= vertex2(1)
ans =
     0
>> points(2) ~= vertex2(2)
ans =
     1   % <-- It means 24.0000 is not equal to 24.0000?

What is the problem?

More surprisingly, I made a new script that has only these commands:

points = [12.0000   15.0000
          33.0000   24.0000
          33.0000   24.0000];

vertex1 = [12 ;  15];
vertex2 = [33 ;  24];

points = points((points(:,1) ~= vertex1(1)) | (points(:,2) ~= vertex1(2)), :);
points = points((points(:,1) ~= vertex2(1)) | (points(:,2) ~= vertex2(2)), :);

The result as expected:

>> points
points =  
   Empty matrix: 0-by-2