public function testDescribe()
{
$X = [1, 2, 3, 4, 5];
$Y = [2, 3, 4, 4, 6];
$stats = Correlation::describe($X, $Y);
$this->assertTrue(is_array($stats));
$this->assertArrayHasKey('cov', $stats);
$this->assertArrayHasKey('r', $stats);
$this->assertArrayHasKey('R2', $stats);
$this->assertArrayHasKey('tau', $stats);
$this->assertArrayHasKey('rho', $stats);
$this->assertTrue(is_numeric($stats['cov']));
$this->assertTrue(is_numeric($stats['r']));
$this->assertTrue(is_numeric($stats['R2']));
$this->assertTrue(is_numeric($stats['tau']));
$this->assertTrue(is_numeric($stats['rho']));
}