| <?php |
| /** |
| * File containing the abstract ezcGraphPolynom class |
| * |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| * |
| * @package Graph |
| * @version //autogentag// |
| * @license http://www.apache.org/licenses/LICENSE-2.0 Apache License, Version 2.0 |
| */ |
| |
| /** |
| * Provides a class for generic operations on polynoms |
| * |
| * This class is mainly used for internal representation of polynoms in the |
| * average dataset ezcGraphDataSetAveragePolynom. |
| * |
| * It provides only very basic mechanisms to work with polynoms, like adding of |
| * polynomes and evaluating the polynom with a given number, to calculate a |
| * point in the chart for a given value on the x axis. |
| * |
| * Beside this the __toString implementation may be used to echo the polynoms |
| * calculated by the least squares mechanism in the above mentioned average |
| * datasets. The class does not provide any options to customize the output. |
| * |
| * The class can be used like: |
| * |
| * <code> |
| * // Equivalent to: x^2 + .5 |
| * $polynom = new ezcGraphPolynom( array( 2 => 1, 0 => .5 ) ); |
| * |
| * // Calculate result for x = 1, echos: 1.5 |
| * echo $polynom->evaluate( 1 ), PHP_EOL; |
| * |
| * // Build the sum with another polynom |
| * $polynom->add( new ezcGraphPolynom( array( 1 => 1 ) ) ); |
| * |
| * // Print polynom, echos: |
| * // x^2 + x + 5.00e-1 |
| * echo $polynom, PHP_EOL; |
| * </code> |
| * |
| * @version //autogentag// |
| * @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 ); |
| } |
| } |
| ?> |