public function testGradientDescent()
{
$xs = array(array(1, 2, 2, 2), array(1, 3, 3, 3), array(1, 4, 4, 4), array(1, 5, 5, 5));
$ys = array(6, 9, 12, 15);
$parameters = array(0, 0, 0, 0);
$gd = new LL_GradientDescent_Regression($xs, $ys, $parameters);
$gd->setLearningRate(0.01);
$gd->setRepetitions(10000);
$gd->train();
$results = $gd->getParameters();
$this->assertLessThan(0.01, array_shift($results));
foreach ($results as $coefficient) {
$this->assertGreaterThan(0.999, $coefficient);
}
$gd->reset();
$gd->setLearningRate(0.03);
$gd->setRepetitions(5);
$results = $gd->train();
$this->assertLessThan(0.3, array_shift($results));
$this->assertGreaterThan(0.2, array_shift($results));
foreach ($results as $coefficient) {
$this->assertGreaterThan(0.99, $coefficient);
}
}
protected function hypothesis($row = null)
{
return $this->sigmoid(parent::hypothesis($row));
}
function __construct($xs, $ys, $initialParameters = null)
{
parent::__construct($xs, $ys, $initialParameters);
$this->setBadIterationsThreshold(100);
// set a higher default ootb.
}