EZ-Components

2026-07-24 10:22:18 +00:00 · 2009-02-17 15:27:43 +00:00
parent 359c3c55c9
commit 0a8e90a8b3
572 changed files with 64490 additions and 0 deletions
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+<?php
+/**
+ * File containing the abstract ezcGraphPolynom class
+ *
+ * @package Graph
+ * @version 1.3
+ * @copyright Copyright (C) 2005-2008 eZ systems as. All rights reserved.
+ * @license http://ez.no/licenses/new_bsd New BSD License
+ */
+/**
+ * Provides a class for generic operations on polynoms
+ *
+ * @version 1.3
+ * @package Graph
+ */
+class ezcGraphPolynom
+{
+    /**
+     * Factors of the polynom
+     *
+     * An example:
+     *  Polynom:
+     *      2 * x^3 + .5 * x - 3
+     *  Array:
+     *      array (
+     *          (int) 3 => (float) 2,
+     *          (int) 1 => (float) .5,
+     *          (int) 0 => (float) -3,
+     *      )
+     * 
+     * @var array
+     */
+    protected $values;
+
+    // @TODO: Introduce precision option for string output?
+
+    /**
+     * 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;
+            }
+
+            $string .= ( $factor < 0 ? ' - ' : ' + ' );
+
+            $factor = abs( $factor );
+            switch ( true )
+            {
+                case abs( 1 - $factor ) < .0001:
+                    // No not append, if factor is ~1
+                    break;
+                case $factor < 1:
+                case $factor >= 1000:
+                    $string .= sprintf( '%.2e ', $factor );
+                    break;
+                case $factor >= 100:
+                    $string .= sprintf( '%.0f ', $factor );
+                    break;
+                case $factor >= 10:
+                    $string .= sprintf( '%.1f ', $factor );
+                    break;
+                default:
+                    $string .= sprintf( '%.2f ', $factor );
+                    break;
+            }
+
+            switch ( true )
+            {
+                case $exponent > 1:
+                    $string .= sprintf( 'x^%d', $exponent );
+                    break;
+                case $exponent === 1:
+                    $string .= 'x';
+                    break;
+                case $exponent === 0:
+                    if ( abs( 1 - $factor ) < .0001 )
+                    {
+                        $string .= '1';
+                    }
+                    break;
+            }
+        }
+
+        if ( substr( $string, 0, 3 ) === ' + ' )
+        {
+            $string = substr( $string, 3 );
+        }
+        else
+        {
+            $string = '-' . substr( $string, 3 );
+        }
+
+        return trim( $string );
+    }
+}
+?>