public function testInitCentroids()
{
$xs = array(array(1, 2, 3, 4), array(4, 2, 5, 1), array(9, 1, 5, 4), array(2, 5, 2, 1), array(9, 9, 11, 12), array(99, 1, 1, 2), array(44, 21, 41, 2));
$shown_up = array();
for ($i = 0; $i < 300; $i++) {
$centroids = _ll_init_centroids($xs, 2);
foreach ($centroids as $centroid) {
// make sure they were assigned to points that exist.
$position = array_search($centroid, $xs);
$this->assertTrue($position !== false);
$shown_up[$position] = true;
}
$this->assertEquals(count($centroids), 2);
$this->assertFalse(_ll_init_centroids($xs, 100));
}
$this->assertTrue(count($shown_up) == count($xs), "Some \$xs did not show up in 300 samples (shown up = " . count($shown_up) . ", xs = " . count($xs) . ".");
}
function ll_kmeans($xs, $k)
{
if ($k > count($xs)) {
return false;
}
$centroids = _ll_init_centroids($xs, $k);
$belongs_to = array();
do {
for ($i = 0; $i < count($xs); $i++) {
// I reversed the order here (to store the centroids as indexes in the array)
// for complexity reasons.
$belongs_to[_ll_closest_centroid($xs[$i], $centroids)][] = $i;
}
$old_centroids = $centroids;
$centroids = _ll_reposition_centroids($centroids, $belongs_to, $xs);
$continue = $old_centroids == $centroids;
} while ($continue);
return $belongs_to;
}
