/**
* Find and return an array of the minimums of the Polynomial
*
* By default the method returns all minimums, if you want the minimums
* within an interval, pass in the $x_min and $x_max parameters.
*
* @access public
*
* @see Math_PolynomialOp::getLocalMaximums()
*
* @param object $p
* @param float $x_min
* @param float $x_max
* @return array
*/
function getLocalMinimums($p, $x_min = null, $x_max = null)
{
if (!is_a($p, 'Math_Polynomial')) {
$p = new Math_Polynomial($p);
}
$mins = array();
$der = Math_PolynomialOp::getDerivative($p);
foreach (Math_PolynomialOp::getRoots($der) as $critical) {
if (Math_PolynomialOp::evaluate($der, $critical - 0.1) < 0 && Math_PolynomialOp::evaluate($der, $critical + 0.1) > 0) {
// Check if its a min.
$mins[] = $critical;
}
}
if ($x_min && $x_max) {
foreach ($mins as $key => $min) {
if ($min < $x_min || $min > $x_max) {
unset($mins[$key]);
}
}
}
return $mins;
}
function testGetRootsQuadratic()
{
$p = new Math_Polynomial('2x^2 + 7x - 4');
$roots = Math_PolynomialOp::getRoots($p);
$this->assertEquals(array(0.5, -4), $roots);
}
