trendClass.php

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<?php

require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/linearBestFitClass.php';
require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/logarithmicBestFitClass.php';
require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/exponentialBestFitClass.php';
require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/powerBestFitClass.php';
require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/polynomialBestFitClass.php';


class trendClass
{
        const TREND_LINEAR                              = 'Linear';
        const TREND_LOGARITHMIC                 = 'Logarithmic';
        const TREND_EXPONENTIAL                 = 'Exponential';
        const TREND_POWER                               = 'Power';
        const TREND_POLYNOMIAL_2                = 'Polynomial_2';
        const TREND_POLYNOMIAL_3                = 'Polynomial_3';
        const TREND_POLYNOMIAL_4                = 'Polynomial_4';
        const TREND_POLYNOMIAL_5                = 'Polynomial_5';
        const TREND_POLYNOMIAL_6                = 'Polynomial_6';
        const TREND_BEST_FIT                    = 'Bestfit';
        const TREND_BEST_FIT_NO_POLY    = 'Bestfit_no_Polynomials';

        private static $_trendTypes = array( self::TREND_LINEAR,
                                                                                 self::TREND_LOGARITHMIC,
                                                                                 self::TREND_EXPONENTIAL,
                                                                                 self::TREND_POWER
                                                                           );
        private static $_trendTypePolyOrders = array( self::TREND_POLYNOMIAL_2,
                                                                                                  self::TREND_POLYNOMIAL_3,
                                                                                                  self::TREND_POLYNOMIAL_4,
                                                                                                  self::TREND_POLYNOMIAL_5,
                                                                                                  self::TREND_POLYNOMIAL_6
                                                                                            );

        private static $_trendCache = array();


        public static function calculate($trendType=self::TREND_BEST_FIT, $yValues, $xValues=array(), $const=True) {
                //      Calculate number of points in each dataset
                $nY = count($yValues);
                $nX = count($xValues);

                //      Define X Values if necessary
                if ($nX == 0) {
                        $xValues = range(1,$nY);
                        $nX = $nY;
                } elseif ($nY != $nX) {
                        //      Ensure both arrays of points are the same size
                        trigger_error("trend(): Number of elements in coordinate arrays do not match.", E_USER_ERROR);
                }

                $key = md5($trendType.$const.serialize($yValues).serialize($xValues));
                //      Determine which trend method has been requested
                switch ($trendType) {
                        //      Instantiate and return the class for the requested trend method
                        case self::TREND_LINEAR :
                        case self::TREND_LOGARITHMIC :
                        case self::TREND_EXPONENTIAL :
                        case self::TREND_POWER :
                                if (!isset(self::$_trendCache[$key])) {
                                        $className = 'PHPExcel_'.$trendType.'_Best_Fit';
                                        self::$_trendCache[$key] = new $className($yValues,$xValues,$const);
                                }
                                return self::$_trendCache[$key];
                                break;
                        case self::TREND_POLYNOMIAL_2   :
                        case self::TREND_POLYNOMIAL_3   :
                        case self::TREND_POLYNOMIAL_4   :
                        case self::TREND_POLYNOMIAL_5   :
                        case self::TREND_POLYNOMIAL_6   :
                                if (!isset(self::$_trendCache[$key])) {
                                        $order = substr($trendType,-1);
                                        self::$_trendCache[$key] = new PHPExcel_Polynomial_Best_Fit($order,$yValues,$xValues,$const);
                                }
                                return self::$_trendCache[$key];
                                break;
                        case self::TREND_BEST_FIT                       :
                        case self::TREND_BEST_FIT_NO_POLY       :
                                //      If the request is to determine the best fit regression, then we test each trend line in turn
                                //      Start by generating an instance of each available trend method
                                foreach(self::$_trendTypes as $trendMethod) {
                                        $className = 'PHPExcel_'.$trendMethod.'BestFit';
                                        $bestFit[$trendMethod] = new $className($yValues,$xValues,$const);
                                        $bestFitValue[$trendMethod] = $bestFit[$trendMethod]->getGoodnessOfFit();
                                }
                                if ($trendType != self::TREND_BEST_FIT_NO_POLY) {
                                        foreach(self::$_trendTypePolyOrders as $trendMethod) {
                                                $order = substr($trendMethod,-1);
                                                $bestFit[$trendMethod] = new PHPExcel_Polynomial_Best_Fit($order,$yValues,$xValues,$const);
                                                if ($bestFit[$trendMethod]->getError()) {
                                                        unset($bestFit[$trendMethod]);
                                                } else {
                                                        $bestFitValue[$trendMethod] = $bestFit[$trendMethod]->getGoodnessOfFit();
                                                }
                                        }
                                }
                                //      Determine which of our trend lines is the best fit, and then we return the instance of that trend class
                                arsort($bestFitValue);
                                $bestFitType = key($bestFitValue);
                                return $bestFit[$bestFitType];
                                break;
                        default :
                                return false;
                }
        }       //      function calculate()

}       //      class trendClass