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<?php
/**
* File containing the abstract ezcGraphPolynom class
*
* @package Graph
* @version //autogentag//
* @copyright Copyright (C) 2005, 2006 eZ systems as. All rights reserved.
* @license http://ez.no/licenses/new_bsd New BSD License
* @access private
*/
/**
* Provides a class for generic operations on polynoms
*
* @package Graph
* @access private
*/
class ezcGraphPolynom
{
protected $values;
/**
* Constructor
*
* Constructs a polynom object from given array, where the key is the
* exponent and the value the factor.
* An example:
* Polynom:
* 2 * x^3 + .5 * x - 3
* Array:
* array (
* (int) 3 => (float) 2,
* (int) 1 => (float) .5,
* (int) 0 => (float) -3,
* )
*
* @param array $values Array with values
* @return ezcGraphPolynom
*/
public function __construct( array $values = array() )
{
foreach ( $values as $exponent => $factor )
{
$this->values[(int) $exponent] = (float) $factor;
}
}
/**
* Initialise a polygon
*
* Initialise a polygon of the given order. Sets all factors to 0.
*
* @param int $order Order of polygon
* @return ezcGraphPolynom Created polynom
*/
public function init( $order )
{
for ( $i = 0; $i <= $order; ++$i )
{
$this->values[$i] = 0;
}
return $this;
}
/**
* Return factor for one exponent
*
* @param int $exponent Exponent
* @return float Factor
*/
public function get( $exponent )
{
if ( !isset( $this->values[$exponent] ) )
{
return 0;
}
else
{
return $this->values[$exponent];
}
}
/**
* Set the factor for one exponent
*
* @param int $exponent Exponent
* @param float $factor Factor
* @return ezcGraphPolynom Modified polynom
*/
public function set( $exponent, $factor )
{
$this->values[(int) $exponent] = (float) $factor;
return $this;
}
/**
* Returns the order of the polynom
*
* @return int Polynom order
*/
public function getOrder()
{
return max( array_keys( $this->values ) );
}
/**
* Adds polynom to current polynom
*
* @param ezcGraphPolynom $polynom Polynom to add
* @return ezcGraphPolynom Modified polynom
*/
public function add( ezcGraphPolynom $polynom )
{
$order = max(
$this->getOrder(),
$polynom->getOrder()
);
for ( $i = 0; $i <= $order; ++$i )
{
$this->set( $i, $this->get( $i ) + $polynom->get( $i ) );
}
return $this;
}
/**
* Evaluate Polynom with a given value
*
* @param float $x Value
* @return float Result
*/
public function evaluate( $x )
{
$value = 0;
foreach ( $this->values as $exponent => $factor )
{
$value += $factor * pow( $x, $exponent );
}
return $value;
}
/**
* Returns a string represenation of the polynom
*
* @return string String representation of polynom
*/
public function __toString()
{
krsort( $this->values );
$string = '';
foreach ( $this->values as $exponent => $factor )
{
if ( $factor == 0 )
{
continue;
}
elseif ( $factor != 1 )
{
$string .= sprintf( '%.2f * ', $factor );
}
$string .= ( $exponent > 1 ? sprintf( 'x^%d + ', $exponent ) :
( $exponent === 1 ? 'x + ' : '' )
);
}
return substr( $string, 0, -3 );
}
}
?>
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