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<?php |
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namespace Kmeans; |
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use Kmeans\Cluster; |
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use Kmeans\ClusterCollection; |
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use Kmeans\Interfaces\AlgorithmInterface; |
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use Kmeans\Interfaces\ClusterCollectionInterface; |
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use Kmeans\Interfaces\ClusterInterface; |
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use Kmeans\Interfaces\InitializationSchemeInterface; |
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use Kmeans\Interfaces\PointCollectionInterface; |
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use Kmeans\Interfaces\PointInterface; |
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abstract class Algorithm implements AlgorithmInterface |
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{ |
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private InitializationSchemeInterface $initScheme; |
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/** |
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* @var array<callable> |
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*/ |
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private array $iterationCallbacks = []; |
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public function __construct(InitializationSchemeInterface $initScheme) |
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{ |
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$this->initScheme = $initScheme; |
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} |
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public function registerIterationCallback(callable $callback): void |
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{ |
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$this->iterationCallbacks[] = $callback; |
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} |
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public function fit( |
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PointCollectionInterface $points, |
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int $nClusters, |
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?int $maxIter = null |
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): ClusterCollectionInterface { |
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$maxIter ??= INF; |
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if ($maxIter < 1) { |
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throw new \UnexpectedValueException( |
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"Invalid maximum number of iterations: {$maxIter}" |
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); |
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} |
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// initialize clusters |
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$clusters = $this->initScheme->initializeClusters($points, $nClusters); |
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// iterate until convergence is reached |
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do { |
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$this->invokeIterationCallbacks($clusters); |
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} while ($this->iterate($clusters) && --$maxIter); |
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// clustering is done. |
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return $clusters; |
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} |
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protected function iterate(ClusterCollectionInterface $clusters): bool |
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{ |
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/** @var \SplObjectStorage<ClusterInterface, null> */ |
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$changed = new \SplObjectStorage(); |
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// calculate proximity amongst points and clusters |
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foreach ($clusters as $cluster) { |
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foreach ($cluster->getPoints() as $point) { |
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// find the closest cluster |
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$closest = $this->getClosestCluster($clusters, $point); |
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if ($closest !== $cluster) { |
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// move the point from its current cluster to its closest |
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$cluster->detach($point); |
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$closest->attach($point); |
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// flag both clusters as changed |
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$changed->attach($cluster); |
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$changed->attach($closest); |
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} |
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} |
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} |
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// update changed clusters' centroid |
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foreach ($changed as $cluster) { |
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$cluster->setCentroid($this->findCentroid($cluster->getPoints())); |
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} |
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// return true if something changed during this iteration |
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return count($changed) > 0; |
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} |
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private function getClosestCluster(ClusterCollectionInterface $clusters, PointInterface $point): ClusterInterface |
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{ |
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$min = INF; |
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$closest = null; |
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foreach ($clusters as $cluster) { |
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$distance = $this->getDistanceBetween($point, $cluster->getCentroid()); |
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if ($distance < $min) { |
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$min = $distance; |
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$closest = $cluster; |
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} |
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} |
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assert($closest !== null); |
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return $closest; |
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} |
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private function invokeIterationCallbacks(ClusterCollectionInterface $clusters): void |
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{ |
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foreach ($this->iterationCallbacks as $callback) { |
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$callback($this, $clusters); |
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} |
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} |
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} |
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bdelespierre /
php-kmeans
