/**
* Ralston and Rabinowitz method for calculate double root (twin root).
*
* @param callback $fxFunction Callback f(x) equation function or
* object/method tuple.
* @param callback $dxFunction Callback f'(x) equation function or
* object/method tuple.
* @param float $xR0 First initial guess.
* @param float $xR1 Second initial guess.
*
* @return float|PEAR_Error Root value on success or PEAR_Error on failure.
* @access public
* @see Math_Numerical_RootFinding_Common::validateEqFunction()
* @see Math_Numerical_RootFinding_Common::getEqResult()
* @see Math_Numerical_RootFinding_Common::isDivergentRow()
* @see Math_Numerical_RootFinding_Secant::compute()
*/
function compute($fxFunction, $dxFunction, $xR0, $xR1)
{
// Validate f(x) equation function.
$err = Math_Numerical_RootFinding_Common::validateEqFunction($fxFunction);
if (PEAR::isError($err)) {
return $err;
}
// Validate f'(x) equation function.
$err = Math_Numerical_RootFinding_Common::validateEqFunction($dxFunction);
if (PEAR::isError($err)) {
return $err;
}
// Sets maximum iteration and tolerance from options.
$maxIteration = $this->options['max_iteration'];
$errTolerance = $this->options['err_tolerance'];
// Sets variable for saving errors during iteration, for divergent
// detection.
$epsErrors = array();
for ($i = 1; $i <= $maxIteration; $i++) {
// Calculate f(x[i-1]) and f'(x[1]), where: x[i-1] = $xR0.
$fxR0 = Math_Numerical_RootFinding_Common::getEqResult($fxFunction, $xR0);
$dxR0 = Math_Numerical_RootFinding_Common::getEqResult($dxFunction, $xR0);
// Calculate f(x[i]) and f'(x[1]), where: x[i] = $xR1.
$fxR1 = Math_Numerical_RootFinding_Common::getEqResult($fxFunction, $xR1);
$dxR1 = Math_Numerical_RootFinding_Common::getEqResult($dxFunction, $xR1);
// Calculate f(x[i-1]) / f'(x[i-1], where x[i-1] = $xR0.
$uxR0 = $fxR0 / $dxR0;
// Calculate f(x[i]) / f'(x[i]), where x[i] = $xR1;
$uxR1 = $fxR1 / $dxR1;
// Avoid division by zero.
if ($uxR0 - $uxR1 == 0) {
return PEAR::raiseError('Iteration skipped division by zero');
}
// Ralston and Rabinowitz's formula.
$xN = $xR1 - $uxR1 * ($xR0 - $xR1) / ($uxR0 - $uxR1);
// xR is the root.
if ($xN == 0) {
$this->root = $xR;
break;
}
// Compute error.
$this->epsError = abs(($xN - $xR1) / $xN);
$epsErrors[] = $this->epsError;
// Detect for divergent rows.
if ($this->isDivergentRows($epsErrors) && $this->options['divergent_skip']) {
return PEAR::raiseError('Iteration skipped, divergent rows detected');
break;
}
// Check for error tolerance, if lower than or equal with
// $errTolerance it is the root.
if ($this->epsError <= $errTolerance) {
$this->root = $xR1;
break;
}
// Swicth the values for next iteration x[i] -> x[i-1] and
// x[i+1] -> x[i], where: x[i-1] = $xR0, x[i] = $xR1, and
// x[i+1] = $xN.
$xR0 = $xR1;
$xR1 = $xN;
}
$this->iterationCount = $i;
return $this->root;
}
/**
* Netwon-Raphson method.
*
* @param callback $fxFunction Callback f(x) equation function or object/method
* tuple.
* @param callback $dfxFunction Callback f'(x) equation function or object/method
* tuple.
* @param float $xR Initial guess.
*
* @return float|PEAR_Error Root value on success or PEAR_Error on failure.
* @access public
* @see Math_Numerical_RootFinding_Common::validateEqFunction()
* @see Math_Numerical_RootFinding_Common::getEqResult()
* @see Math_Numerical_RootFinding_Common::isDivergentRow()
* @see Math_Numerical_RootFinding_NewtonRaphson2::compute()
*/
public function compute($fxFunction, $dfxFunction, $xR)
{
// evaluate f(x) equation function before begin anything
parent::validateEqFunction($fxFunction, $xR);
// evaluate df(x) equation function before begin anything
parent::validateEqFunction($dfxFunction, $xR);
// Sets maximum iteration and tolerance from options.
$maxIteration = $this->options['max_iteration'];
$errTolerance = $this->options['err_tolerance'];
// Sets variable for saving errors during iteration, for divergent
// detection.
$epsErrors = array();
for ($i = 1; $i < $maxIteration; $i++) {
// Calculate f(x[i]), where: x[i] = $xR.
$fxR = parent::getEqResult($fxFunction, $xR);
// Calculate f'(x[i]), where: x[i] = $xR.
$dxR = parent::getEqResult($dfxFunction, $xR);
// Avoid division by zero.
if ($dxR == 0) {
throw new \Exception('Iteration skipped, division by zero');
}
// Newton-Raphson's formula.
$xN = $xR - $fxR / $dxR;
// xR is the root.
if ($xN == 0) {
$this->root = $xR;
break;
}
// Compute error.
$this->epsError = abs(($xN - $xR) / $xN);
$epsErrors[] = $this->epsError;
// Detect for divergent rows.
if ($this->isDivergentRows($epsErrors) && $this->options['divergent_skip']) {
throw new \Exception('Iteration skipped, divergent rows detected');
break;
}
// Check for error tolerance, if lower than or equal with
// $errTolerance it is the root.
if ($this->epsError <= $errTolerance) {
$this->root = $xR;
break;
}
// Switch x[i+1] -> x[i], where: x[i] = $xR and x[i+1] = $xN.
$xR = $xN;
}
$this->iterationCount = $i;
return $this->root;
}
/**
* Bisection/Binary Chopping/Interval Halving/Bolzano method.
*
* @param callback $fxFunction Callback f(x) equation function or
* object/method tuple.
* @param float $xL Lower guess.
* @param float $xU Upper guess.
*
* @return float|PEAR_Error Root value on success or PEAR_Error on failure.
* @access public
* @see Math_Numerical_RootFinding::validateEqFunction()
* @see Math_Numerical_RootFinding::getEqResult()
* @see Math_Numerical_RootFinding_Falseposition::compute()
*/
function compute($fxFunction, $xL, $xU)
{
// Validate f(x) equation function.
$err = Math_Numerical_RootFinding_Common::validateEqFunction($fxFunction);
if (PEAR::isError($err)) {
return $err;
}
// Sets first approximation $xR (Bisection's formula).
$xR = ($xU + $xL) / 2;
// Validate f(x) equation function.
$err = Math_Numerical_RootFinding_Common::validateEqFunction($fxFunction);
if (PEAR::isError($err)) {
return $err;
}
// Sets maximum iteration and tolerance from options.
$maxIteration = $this->options['max_iteration'];
$errTolerance = $this->options['err_tolerance'];
// Sets variable for saving errors during iteration, for divergent
// detection.
$epsErrors = array();
for ($i = 0; $i < $maxIteration; $i++) {
// Calculate f(x), where: x = xL and x = xR
$fxL = Math_Numerical_RootFinding_Common::getEqResult($fxFunction, $xL);
$fxR = Math_Numerical_RootFinding_Common::getEqResult($fxFunction, $xR);
if ($fxL * $fxR < 0) {
// Root is at first subinterval.
$xU = $xR;
} elseif ($fxL * $fxR > 0) {
// Root is at second subinterval.
$xL = $xR;
} elseif ($fxL * $fxR == 0) {
// $xR is the exact root.
$this->root = $xR;
break;
}
// Compute new approximation.
$xN = ($xL + $xU) / 2;
// Compute approximation error.
$this->epsError = abs(($xN - $xR) / $xN);
$epsErrors[] = $this->epsError;
// Detect for divergent rows.
if ($this->isDivergentRows($epsErrors) && $this->options['divergent_skip']) {
return PEAR::raiseError('Iteration skipped, divergent rows detected');
break;
}
// Check for error tolerance, if lower than or equal with
// $errTolerance it is the root.
if ($this->epsError <= $errTolerance) {
$this->root = $xN;
break;
}
// Switch xn -> xr, where xn = $xN and xr = $xR.
$xR = $xN;
}
$this->iterationCount = $i;
return $this->root;
}
/**
* Fixed Point method.
*
* This method using g(x) (the modification of f(x), which g(x) = x).
*
* @param callback $gxFunction Callback g(x) equation function or object/method
* tuple.
* @param float $xR Initial guess.
*
* @return float|PEAR_Error Root value on success or PEAR_Error on failure.
* @access public
* @see Math_Numerical_RootFinding_Common::validateEqFunction()
* @see Math_Numerical_RootFinding_Common::getEqResult()
* @see Math_Numerical_RootFinding_Common::isDivergentRow()
*/
public function compute($gxFunction, $xR)
{
// Validate g(x) equation function.
parent::validateEqFunction($gxFunction, $xR);
// Sets maximum iteration and tolerance from options.
$maxIteration = $this->options['max_iteration'];
$errTolerance = $this->options['err_tolerance'];
// Sets variable for saving errors during iteration, for divergent
// detection.
$epsErrors = array();
for ($i = 0; $i < $maxIteration; $i++) {
// Calculate g(x[i]), where x[i] = $xR (Fixed Point's formula).
$xN = parent::getEqResult($gxFunction, $xR);
// xR is the root.
if ($xN == 0) {
$this->root = $xR;
break;
}
// Compute error.
$this->epsError = abs(($xN - $xR) / $xN);
$epsErrors[] = $this->epsError;
// Detect for divergent rows.
if ($this->isDivergentRows($epsErrors) && $this->options['divergent_skip']) {
throw new \Exception('Iteration skipped, divergent rows detected');
break;
}
// Check for error tolerance, if lower than or equal with
// $errTolerance it is the root.
if ($this->epsError <= $errTolerance) {
$this->root = $xR;
break;
}
// Switch x[i+1] -> x[i], where: x[i] = $xR and x[i+1] = $xN.
$xR = $xN;
}
$this->iterationCount = $i;
return $this->root;
}
/**
* Newton-Raphson method for calculate double root (twin root).
*
* @param callback $fxFunction Callback f(x) equation function or
* object/method tuple.
* @param callback $dfx1Function Callback f'(x) equation function or
* object/method tuple.
* @param callback $dfx2Function Callback f''(x) equation function or
* object/method tuple.
* @param float $xR Initial guess.
*
* @return float|PEAR_Error Root value on success or PEAR_Error on failure.
* @access public
* @see Math_Numerical_RootFinding_Common::validateEqFunction()
* @see Math_Numerical_RootFinding_Common::getEqResult()
* @see Math_Numerical_RootFinding_Common::isDivergentRow()
* @see Math_Numerical_RootFinding_Newtonraphson::compute()
*/
function compute($fxFunction, $dfx1Function, $dfx2Function, $xR)
{
// Validate f(x) equation function.
$err = Math_Numerical_RootFinding_Common::validateEqFunction($fxFunction);
if (PEAR::isError($err)) {
return $err;
}
// Validate f'(x) equation function.
$err = Math_Numerical_RootFinding_Common::validateEqFunction($dfx1Function);
if (PEAR::isError($err)) {
return $err;
}
// Validate f''(x) equation function.
$err = Math_Numerical_RootFinding_Common::validateEqFunction($dfx2Function);
if (PEAR::isError($err)) {
return $err;
}
// Sets maximum iteration and tolerance from options.
$maxIteration = $this->options['max_iteration'];
$errTolerance = $this->options['err_tolerance'];
// Sets variable for saving errors during iteration, for divergent
// detection.
$epsErrors = array();
for ($i = 1; $i < $maxIteration; $i++) {
// Calculate f(x[i]), where: x[i] = $xR.
$fxR = Math_Numerical_RootFinding_Common::getEqResult($fxFunction, $xR);
// Calculate f'(x[i]), where: x[i] = $xR.
$d1xR = Math_Numerical_RootFinding_Common::getEqResult($dfx1Function, $xR);
// Calculate f''(x[i]), where: x[i] = $xR.
$d2xR = Math_Numerical_RootFinding_Common::getEqResult($dfx2Function, $xR);
// Avoid division by zero.
if (pow($d1xR, 2) - $fxR * $d2xR == 0) {
return PEAR::raiseError('Iteration skipped, division by zero');
}
// Newton-Raphson's formula.
$xN = $xR - $fxR * $d1xR / (pow($d1xR, 2) - $fxR * $d2xR);
// xR is the root.
if ($xN == 0) {
$this->root = $xR;
break;
}
// Compute error.
$this->epsError = abs(($xN - $xR) / $xN);
$epsErrors[] = $this->epsError;
// Detect for divergent rows.
if ($this->isDivergentRows($epsErrors) && $this->options['divergent_skip']) {
return PEAR::raiseError('Iteration skipped, divergent rows detected');
break;
}
// Check for error tolerance, if lower than or equal with
// $errTolerance it is the root.
if ($this->epsError <= $errTolerance) {
$this->root = $xR;
break;
}
// Switch x[i+1] -> x[i], where: x[i] = $xR and x[i+1] = $xN.
$xR = $xN;
}
$this->iterationCount = $i;
return $this->root;
}
/**
* Secant method.
*
* @param callback $fxFunction Callback f(x) equation function or object/method
* tuple.
* @param float $xR0 First initial guess.
* @param float $xR1 Second initial guess.
*
* @return float|PEAR_Error Root value on success or PEAR_Error on failure.
* @access public
* @see Math_Numerical_RootFinding_Common::validateEqFunction()
* @see Math_Numerical_RootFinding_Common::getEqResult()
* @see Math_Numerical_RootFinding_Common::isDivergentRow()
* @see Math_Numerical_RootFinding_Ralstonrabinowitz::compute()
*/
public function compute($fxFunction, $xR0, $xR1)
{
// Validate f(x) equation function.
parent::validateEqFunction($fxFunction, $xR0);
// Sets maximum iteration and tolerance from options.
$maxIteration = $this->options['max_iteration'];
$errTolerance = $this->options['err_tolerance'];
// Sets variable for saving errors during iteration, for divergent
// detection.
$epsErrors = array();
for ($i = 1; $i <= $maxIteration; $i++) {
// Calculate f(x[i-1]), where: x[i-1] = $xR0.
$fxR0 = parent::getEqResult($fxFunction, $xR0);
// Calculate f(x[i]), where: x[i] = $xR1.
$fxR1 = parent::getEqResult($fxFunction, $xR1);
// Avoid division by zero.
if ($fxR0 - $fxR1 == 0) {
throw new \Exception('Iteration skipped division by zero');
}
// Secant's formula.
$xN = $xR1 - $fxR1 * ($xR0 - $xR1) / ($fxR0 - $fxR1);
// xR is the root.
if ($xN == 0) {
$this->root = $xR;
break;
}
// Compute error.
$this->epsError = abs(($xN - $xR1) / $xN);
$epsErrors[] = $this->epsError;
// Detect for divergent rows.
if ($this->isDivergentRows($epsErrors) && $this->options['divergent_skip']) {
throw new \Exception('Iteration skipped, divergent rows detected');
break;
}
// Check for error tolerance, if lower than or equal with
// $errTolerance it is the root.
if ($this->epsError <= $errTolerance) {
$this->root = $xR1;
break;
}
// Swicth the values for next iteration x[i] -> x[i-1] and
// x[i+1] -> x[i], where: x[i-1] = $xR0, x[i] = $xR1, and
// x[i+1] = $xN.
$xR0 = $xR1;
$xR1 = $xN;
}
$this->iterationCount = $i;
return $this->root;
}
/**
* Validate equation function or object/method.
*
* Simple function to know the whether equation function or object/method
* callback is working.
*
* @param string $eqFunction Equation function name or object method tuple.
*
* @return bool|PEAR_Error TRUE on success or PEAR_Error on failure.
* @access public
* @see getEqResult()
* @static
*/
function validateEqFunction($eqFunction)
{
$err = Math_Numerical_RootFinding_Common::getEqResult($eqFunction, 1);
if (PEAR::isError($err)) {
return $err;
}
return true;
}
/**
* False Position/Regula Falsi method.
*
* @param callback $fxFunction Callback f(x) equation function or
* object/method tuple.
* @param float $xL Lower guess.
* @param float $xU Upper guess.
*
* @return float|PEAR_Error Root value on success or PEAR_Error on failure.
* @access public
* @see Math_Numerical_RootFinding_Common::validateEqFunction()
* @see Math_Numerical_RootFinding_Common::getEqResult()
* @see Math_Numerical_RootFinding_Bisection::compute()
*/
public function compute($fxFunction, $xL, $xU)
{
// Validate f(x) equation function.
parent::validateEqFunction($fxFunction, $xL);
// Sets maximum iteration and tolerance from options.
$maxIteration = $this->options['max_iteration'];
$errTolerance = $this->options['err_tolerance'];
// Calculate first approximation $xR (False Position's formula).
$fxL = parent::getEqResult($fxFunction, $xL);
$fxU = parent::getEqResult($fxFunction, $xU);
if ($fxL - $fxU == 0) {
throw new \Exception('Iteration skipped, division by zero');
}
$xR = $xU - $fxU * ($xL - $xU) / ($fxL - $fxU);
// Sets variable for saving errors during iteration, for divergent
// detection.
$epsErrors = array();
for ($i = 0; $i < $maxIteration; $i++) {
// Calculate f(xr), where: xr = $xR
$fxR = parent::getEqResult($fxFunction, $xR);
if ($fxL * $fxR < 0) {
// Root is at first subinterval.
$xU = $xR;
} elseif ($fxL * $fxR > 0) {
// Root is at second subinterval.
$xL = $xR;
} elseif ($fxL * $fxR == 0) {
// $xR is the exact root.
$this->root = $xR;
break;
}
// Avoid division by zero.
if ($fxL - $fxU == 0) {
throw new \Exception('Iteration skipped, division by zero');
}
// Compute new approximation.
$xN = $xU - $fxU * ($xL - $xU) / ($fxL - $fxU);
// Compute approximation error.
$this->epsError = abs(($xN - $xR) / $xN);
$epsErrors[] = $this->epsError;
// Detect for divergent rows.
if ($this->isDivergentRows($epsErrors) && $this->options['divergent_skip']) {
throw new \Exception('Iteration skipped, divergent rows detected');
break;
}
// Check for error tolerance, if lower than or equal with
// $errTolerance it is the root.
if ($this->epsError <= $errTolerance) {
$this->root = $xN;
break;
}
// Calculate f(xl), where xl = $xL.
$fxL = parent::getEqResult($fxFunction, $xL);
// Calculate f(xu), where xu = $xU.
$fxU = parent::getEqResult($fxFunction, $xU);
// Switch xn -> xr, where xn = $xN and xr = $xR.
$xR = $xN;
}
$this->iterationCount = $i;
return $this->root;
}