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<?php
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/**
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 * PHPExcel
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 *
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 * Copyright (c) 2006 - 2013 PHPExcel
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 *
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 * This library is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * This library is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with this library; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
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 *
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 * @category   PHPExcel
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 * @package    PHPExcel_Shared_Trend
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 * @copyright  Copyright (c) 2006 - 2013 PHPExcel (http://www.codeplex.com/PHPExcel)
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 * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt	LGPL
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 * @version    ##VERSION##, ##DATE##
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 */
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require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/linearBestFitClass.php';
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require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/logarithmicBestFitClass.php';
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require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/exponentialBestFitClass.php';
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require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/powerBestFitClass.php';
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require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/polynomialBestFitClass.php';
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/**
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 * PHPExcel_trendClass
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 *
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 * @category   PHPExcel
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 * @package    PHPExcel_Shared_Trend
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 * @copyright  Copyright (c) 2006 - 2013 PHPExcel (http://www.codeplex.com/PHPExcel)
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 */
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class trendClass
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{
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	const TREND_LINEAR				= 'Linear';
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	const TREND_LOGARITHMIC			= 'Logarithmic';
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	const TREND_EXPONENTIAL			= 'Exponential';
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	const TREND_POWER				= 'Power';
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	const TREND_POLYNOMIAL_2		= 'Polynomial_2';
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	const TREND_POLYNOMIAL_3		= 'Polynomial_3';
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	const TREND_POLYNOMIAL_4		= 'Polynomial_4';
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	const TREND_POLYNOMIAL_5		= 'Polynomial_5';
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	const TREND_POLYNOMIAL_6		= 'Polynomial_6';
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	const TREND_BEST_FIT			= 'Bestfit';
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	const TREND_BEST_FIT_NO_POLY	= 'Bestfit_no_Polynomials';
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	/**
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	 * Names of the best-fit trend analysis methods
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	 *
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	 * @var string[]
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	 **/
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	private static $_trendTypes = array( self::TREND_LINEAR,
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										 self::TREND_LOGARITHMIC,
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										 self::TREND_EXPONENTIAL,
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										 self::TREND_POWER
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									   );
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	/**
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	 * Names of the best-fit trend polynomial orders
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	 *
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	 * @var string[]
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	 **/
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	private static $_trendTypePolyOrders = array( self::TREND_POLYNOMIAL_2,
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												  self::TREND_POLYNOMIAL_3,
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												  self::TREND_POLYNOMIAL_4,
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												  self::TREND_POLYNOMIAL_5,
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												  self::TREND_POLYNOMIAL_6
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											    );
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	/**
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	 * Cached results for each method when trying to identify which provides the best fit
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	 *
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	 * @var PHPExcel_Best_Fit[]
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	 **/
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	private static $_trendCache = array();
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	public static function calculate($trendType=self::TREND_BEST_FIT, $yValues, $xValues=array(), $const=True) {
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		//	Calculate number of points in each dataset
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		$nY = count($yValues);
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		$nX = count($xValues);
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		//	Define X Values if necessary
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		if ($nX == 0) {
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			$xValues = range(1,$nY);
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			$nX = $nY;
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		} elseif ($nY != $nX) {
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			//	Ensure both arrays of points are the same size
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			trigger_error("trend(): Number of elements in coordinate arrays do not match.", E_USER_ERROR);
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		}
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		$key = md5($trendType.$const.serialize($yValues).serialize($xValues));
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		//	Determine which trend method has been requested
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		switch ($trendType) {
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			//	Instantiate and return the class for the requested trend method
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			case self::TREND_LINEAR :
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			case self::TREND_LOGARITHMIC :
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			case self::TREND_EXPONENTIAL :
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			case self::TREND_POWER :
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				if (!isset(self::$_trendCache[$key])) {
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					$className = 'PHPExcel_'.$trendType.'_Best_Fit';
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					self::$_trendCache[$key] = new $className($yValues,$xValues,$const);
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				}
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				return self::$_trendCache[$key];
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				break;
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			case self::TREND_POLYNOMIAL_2	:
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			case self::TREND_POLYNOMIAL_3	:
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			case self::TREND_POLYNOMIAL_4	:
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			case self::TREND_POLYNOMIAL_5	:
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			case self::TREND_POLYNOMIAL_6	:
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				if (!isset(self::$_trendCache[$key])) {
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					$order = substr($trendType,-1);
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					self::$_trendCache[$key] = new PHPExcel_Polynomial_Best_Fit($order,$yValues,$xValues,$const);
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				}
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				return self::$_trendCache[$key];
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				break;
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			case self::TREND_BEST_FIT			:
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			case self::TREND_BEST_FIT_NO_POLY	:
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				//	If the request is to determine the best fit regression, then we test each trend line in turn
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				//	Start by generating an instance of each available trend method
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				foreach(self::$_trendTypes as $trendMethod) {
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					$className = 'PHPExcel_'.$trendMethod.'BestFit';
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					$bestFit[$trendMethod] = new $className($yValues,$xValues,$const);
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					$bestFitValue[$trendMethod] = $bestFit[$trendMethod]->getGoodnessOfFit();
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				}
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				if ($trendType != self::TREND_BEST_FIT_NO_POLY) {
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					foreach(self::$_trendTypePolyOrders as $trendMethod) {
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						$order = substr($trendMethod,-1);
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						$bestFit[$trendMethod] = new PHPExcel_Polynomial_Best_Fit($order,$yValues,$xValues,$const);
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						if ($bestFit[$trendMethod]->getError()) {
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							unset($bestFit[$trendMethod]);
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						} else {
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							$bestFitValue[$trendMethod] = $bestFit[$trendMethod]->getGoodnessOfFit();
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						}
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					}
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				}
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				//	Determine which of our trend lines is the best fit, and then we return the instance of that trend class
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				arsort($bestFitValue);
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				$bestFitType = key($bestFitValue);
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				return $bestFit[$bestFitType];
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				break;
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			default	:
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				return false;
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		}
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	}	//	function calculate()
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}	//	class trendClass