/**
* Get the roots of this Polynomial
*
* For Polynomials of degree less than or equal to 4, the exact value of any
* real roots (zeros) of the Polynomial are returned. For Polynomials of
* higher degrees, the roots are estimated using the Newton-Raphson method
* from the {@link http://pear.php.net/package/Math_Numerical_RootFinding/
* Math_Numerical_RootFinding} package. Remember that these roots are
* *estimates* and for high-degree polynomials all of the roots may not be
* calculated and returned!
*
* If you're calculating roots for a higher-degree Polynomial and want to
* provide the initial guesses for the roots, you can pass them in as an
* array parameter.
*
* If possible, this function will return integers instead of floats.
*
* @see Math_PolynomialOp::getRootsLinear(), Math_PolynomialOp::getRootsQuadratic(), Math_PolynomialOp::getRootsCubic(), Math_PolynomialOp::getRootsQuartic(), Math_PolynomialOp::getRootsHighDegree(), Math_Numerical_RootFinding
*
* @access public
*
* @param object $p
* @param array $guesses
* @return array An array of roots ( points where y = 0 )
*/
function getRoots($p, $guesses = array())
{
if (!is_a($p, 'Math_Polynomial')) {
$p = new Math_Polynomial($p);
}
if ($p->degree() == 0) {
// Constant
return array();
} else {
if ($p->degree() == 1) {
// Linear
return Math_PolynomialOp::getRootsLinear($p);
} else {
if ($p->degree() == 2) {
// Quadratic
return Math_PolynomialOp::getRootsQuadratic($p);
} else {
if ($p->degree() == 3) {
// Cubic
return Math_PolynomialOp::getRootsCubic($p);
} else {
if ($p->degree() == 4) {
// Quartic
return Math_PolynomialOp::getRootsQuartic($p);
} else {
return Math_PolynomialOp::getRootsHighDegree($p, $guesses);
}
}
}
}
}
}
function testRootsQuartic()
{
$p = new Math_Polynomial('3x^4 + 6x^3 - 123x^2 - 126X + 1080');
$roots = Math_PolynomialOp::getRootsQuartic($p);
$this->assertEquals(array(5, 3, -4, -6), $roots);
}