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POWhy is 24.0000 not equal to 24.0000 in MATLAB?
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copied!<p>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.</p> <p>In the following code, <code>intersections</code> function gets the intersection points:</p> <pre><code>[points(:,1), points(:,2)] = intersections(... obj.modifiedVGVertices(1,:), obj.modifiedVGVertices(2,:), ... [vertex1(1) vertex2(1)], [vertex1(2) vertex2(2)]); </code></pre> <p>The result:</p> <pre><code>>> points points = 12.0000 15.0000 33.0000 24.0000 33.0000 24.0000 >> vertex1 vertex1 = 12 15 >> vertex2 vertex2 = 33 24 </code></pre> <p>Two points (<code>vertex1</code> and <code>vertex2</code>) should be eliminated from the result. It should be done by the below commands:</p> <pre><code>points = points((points(:,1) ~= vertex1(1)) | (points(:,2) ~= vertex1(2)), :); points = points((points(:,1) ~= vertex2(1)) | (points(:,2) ~= vertex2(2)), :); </code></pre> <p>After doing that, we have this unexpected outcome:</p> <pre><code>>> points points = 33.0000 24.0000 </code></pre> <p>The outcome should be an empty matrix. As you can see, the first (or second?) pair of <code>[33.0000 24.0000]</code> has been eliminated, but not the second one.</p> <p>Then I checked these two expressions:</p> <pre><code>>> points(1) ~= vertex2(1) ans = 0 >> points(2) ~= vertex2(2) ans = 1 % <-- It means 24.0000 is not equal to 24.0000? </code></pre> <p>What is the problem?</p> <hr> <p>More surprisingly, I made a new script that has only these commands:</p> <pre><code>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)), :); </code></pre> <p>The result as expected:</p> <pre><code>>> points points = Empty matrix: 0-by-2 </code></pre>

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