/**
* @covers NumbersPHP\Statistic::exponentialRegression
*/
public function testExponentialRegression()
{
$source = array(10, 9, 8, 8, 7, 7, 6, 6.5, 6.4, 6.3, 6.2);
$regressionValues = array(9.077131929916444, 8.669377715385259, 8.279940244595563, 7.907996710352883, 7.552761266818376, 7.213483369166244, 6.8894461878255076, 6.579965093955639, 6.284386212956255, 6.002085042954625, 5.732465135352174);
$exponentialRegression = \NumbersPHP\Statistic::exponentialRegression($source);
$regressionFunction = $exponentialRegression[0];
$regressionRSquared = $exponentialRegression[1];
$this->assertTrue(\NumbersPHP\Basic::numbersEqual($regressionRSquared, 0.8491729985314136));
$regressionFunctionValues = $regressionFunction(\NumbersPHP\Basic::range(1, count($source)));
for ($i = 0; $i < count($regressionValues); ++$i) {
$this->assertTrue(\NumbersPHP\Basic::numbersEqual($regressionValues[$i], $regressionFunctionValues[$i]));
}
$this->assertTrue(\NumbersPHP\Basic::numbersEqual($regressionFunction(1), 9.077131929916444));
$this->assertTrue(\NumbersPHP\Basic::numbersEqual($regressionFunction(15), 4.769782016165231));
}
