polynomialBestFitClass.php

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<?php
require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/bestFitClass.php';
require_once PHPEXCEL_ROOT . 'PHPExcel/Shared/JAMA/Matrix.php';


class PHPExcel_Polynomial_Best_Fit extends PHPExcel_Best_Fit
{
        protected $_bestFitType         = 'polynomial';

        protected $_order                       = 0;


        public function getOrder() {
                return $this->_order;
        }       //      function getOrder()


        public function getValueOfYForX($xValue) {
                $retVal = $this->getIntersect();
                $slope = $this->getSlope();
                foreach($slope as $key => $value) {
                        if ($value != 0.0) {
                                $retVal += $value * pow($xValue, $key + 1);
                        }
                }
                return $retVal;
        }       //      function getValueOfYForX()


        public function getValueOfXForY($yValue) {
                return ($yValue - $this->getIntersect()) / $this->getSlope();
        }       //      function getValueOfXForY()


        public function getEquation($dp=0) {
                $slope = $this->getSlope($dp);
                $intersect = $this->getIntersect($dp);

                $equation = 'Y = '.$intersect;
                foreach($slope as $key => $value) {
                        if ($value != 0.0) {
                                $equation .= ' + '.$value.' * X';
                                if ($key > 0) {
                                        $equation .= '^'.($key + 1);
                                }
                        }
                }
                return $equation;
        }       //      function getEquation()


        public function getSlope($dp=0) {
                if ($dp != 0) {
                        $coefficients = array();
                        foreach($this->_slope as $coefficient) {
                                $coefficients[] = round($coefficient,$dp);
                        }
                        return $coefficients;
                }
                return $this->_slope;
        }       //      function getSlope()


        public function getCoefficients($dp=0) {
                return array_merge(array($this->getIntersect($dp)),$this->getSlope($dp));
        }       //      function getCoefficients()


        private function _polynomial_regression($order, $yValues, $xValues, $const) {
                // calculate sums
                $x_sum = array_sum($xValues);
                $y_sum = array_sum($yValues);
                $xx_sum = $xy_sum = 0;
                for($i = 0; $i < $this->_valueCount; ++$i) {
                        $xy_sum += $xValues[$i] * $yValues[$i];
                        $xx_sum += $xValues[$i] * $xValues[$i];
                        $yy_sum += $yValues[$i] * $yValues[$i];
                }
                /*
                 *      This routine uses logic from the PHP port of polyfit version 0.1
                 *      written by Michael Bommarito and Paul Meagher
                 *
                 *      The function fits a polynomial function of order $order through
                 *      a series of x-y data points using least squares.
                 *
                 */
                for ($i = 0; $i < $this->_valueCount; ++$i) {
                        for ($j = 0; $j <= $order; ++$j) {
                                $A[$i][$j] = pow($xValues[$i], $j);
                        }
                }
                for ($i=0; $i < $this->_valueCount; ++$i) {
                        $B[$i] = array($yValues[$i]);
                }
                $matrixA = new Matrix($A);
                $matrixB = new Matrix($B);
                $C = $matrixA->solve($matrixB);

                $coefficients = array();
                for($i = 0; $i < $C->m; ++$i) {
                        $r = $C->get($i, 0);
                        if (abs($r) <= pow(10, -9)) {
                                $r = 0;
                        }
                        $coefficients[] = $r;
                }

                $this->_intersect = array_shift($coefficients);
                $this->_slope = $coefficients;

                $this->_calculateGoodnessOfFit($x_sum,$y_sum,$xx_sum,$yy_sum,$xy_sum);
                foreach($this->_xValues as $xKey => $xValue) {
                        $this->_yBestFitValues[$xKey] = $this->getValueOfYForX($xValue);
                }
        }       //      function _polynomial_regression()


        function __construct($order, $yValues, $xValues=array(), $const=True) {
                if (parent::__construct($yValues, $xValues) !== False) {
                        if ($order < $this->_valueCount) {
                                $this->_bestFitType .= '_'.$order;
                                $this->_order = $order;
                                $this->_polynomial_regression($order, $yValues, $xValues, $const);
                                if (($this->getGoodnessOfFit() < 0.0) || ($this->getGoodnessOfFit() > 1.0)) {
                                        $this->_error = True;
                                }
                        } else {
                                $this->_error = True;
                        }
                }
        }       //      function __construct()

}       //      class polynomialBestFit