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POC# Sort List of X,Y Coordinates Clockwise
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  1. POC# Sort List of X,Y Coordinates Clockwise
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    copied!<p>I am using .NET 2.0 so I don't have access to the nifty Linq; however, I have worked up some code that sorts a list of points clockwise/counterclockwise.</p> <p>My problem is that the sort works perfectly fine if the list is not already sorted, but if for some reason the list is already sorted the sort function fails miserably.</p> <p>I was wandering if someone could help point me in the right direction as to why this may be the cause.</p> <p>Here is my call to the sort:</p> <pre><code>positions.Sort(new Comparison&lt;Position&gt;(MapUtils.SortCornersClockwise)); </code></pre> <p>And here is the SortCornersClockwise function:</p> <pre><code>public static int SortCornersClockwise( Position A, Position B) { // Variables to Store the atans double aTanA, aTanB; // Reference Point Pixels reference = Program.main.reference; // Fetch the atans aTanA = Math.Atan2(A.Pixel.Y - reference.Y, A.Pixel.X - reference.X); aTanB = Math.Atan2(B.Pixel.Y - reference.Y, B.Pixel.X - reference.X); // Determine next point in Clockwise rotation if (aTanA &lt; aTanB) return -1; else if (aTanB &gt; aTanA) return 1; return 0; } </code></pre> <p>Where my reference is the point from which I determine the respective angle to each point in my list of points.</p> <p>Now say I have a list of points:</p> <pre><code>15778066, 27738237 15778169, 27738296 15778185, 27738269 15778082, 27738210 </code></pre> <p>These are already sorted in the correct order but calling the sort function yields:</p> <pre><code>15778082, 27738210 15778066, 27738237 15778185, 27738269 15778169, 27738296 </code></pre> <p>Now take another set of sample points:</p> <pre><code>15778180, 27738255 15778081, 27738192 15778064, 27738219 15778163, 27738282 </code></pre> <p>This list is not already in the correct order and calling the sort function yields:</p> <pre><code>15778064, 27738219 15778081, 27738192 15778180, 27738255 15778163, 27738282 </code></pre> <p>Which is sorted correctly. This pattern repeats it self for each set of coordinates that are already sorted and for those that aren't. Any ideas?</p>
 

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