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copied!<p>I'm not familiar with software libraries for this problem. but if you are talking in 2D space, then here is some math that comes to my mind:</p> <p>you can find the distance of any 2 points in the 2D space using this calculation:</p> <p>distance = sqrt( (X2 - X1)^2 + (Y2 - Y1 )^2 )</p> <p>inwhich ^2 means powered by 2.</p> <p>so le'ts say you have an array of Point objects (here I define a simple class for Points), this way you can find out which points are neighbored:</p> <pre><code>class Point { protected $_x = 0; protected $_y = 0; public function __construct($x,$y) { $this->_x = $x; $this->_y = $y; } public function getX() { return $this->_x; } public function getY() { return $this->_y; } public function getDistanceFrom($x,$y) { $distance = sqrt( pow($x - $this->_x , 2) + pow($y - $this->_y , 2) ); return $distance; } public function isCloseTo($point=null,$threshold=10) { $distance = $this->getDistanceFrom($point->getX(), $point->getY() ); if ( abs($distance) <= $threshold ) return true; return false; } public function addNeighbor($point) { array_push($this->_neighbors,$point); return count($this->_neighbors); } public function getNeighbors() { return $this->_neighors; } } $threshold = 100; // the threshold that if 2 points are closer than it, they are called "close" in our application $pointList = array(); /* * here you populate your point objects into the $pointList array. */ // you have your coordinates, right? $myPoint = new Point($myXCoordinate, $myYCoordinate); foreach ($pointList as $point) { if ($myPoint->isCloseTo($point,$threshold) { $myPoint->addNeighbor($point); } } $nearbyPointsList = $myPoint->getNeighbors(); </code></pre> <p>edit: I'm sorry, I had forgotten the linear distance formula. both X and Y axis distance values should be powered by 2 and then the sqrt of their sum is the result. the code is now corrected.</p>

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