File Source for logarithmicBestFitClass.php

<?php
/**
* PHPExcel
*
* Copyright (c) 2006 - 2011 PHPExcel
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* @category PHPExcel
* @package PHPExcel_Shared_Best_Fit
* @copyright Copyright (c) 2006 - 2011 PHPExcel (http://www.codeplex.com/PHPExcel)
* @license http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt LGPL
* @version 1.7.6, 2011-02-27
*/
require_once(PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/bestFitClass.php');
/**
* PHPExcel_Logarithmic_Best_Fit
*
* @category PHPExcel
* @package PHPExcel_Shared_Best_Fit
* @copyright Copyright (c) 2006 - 2011 PHPExcel (http://www.codeplex.com/PHPExcel)
*/
class PHPExcel_Logarithmic_Best_Fit extends PHPExcel_Best_Fit
{
protected $_bestFitType = 'logarithmic';
public function getValueOfYForX($xValue) {
return $this->getIntersect() + $this->getSlope() * log($xValue - $this->_Xoffset);
} // function getValueOfYForX()
public function getValueOfXForY($yValue) {
return exp(($yValue - $this->getIntersect()) / $this->getSlope());
} // function getValueOfXForY()
public function getEquation($dp=0) {
$slope = $this->getSlope($dp);
$intersect = $this->getIntersect($dp);
return 'Y = '.$intersect.' + '.$slope.' * log(X)';
} // function getEquation()
private function _logarithmic_regression($yValues, $xValues, $const) {
foreach($xValues as &$value) {
if ($value < 0.0) {
$value = 0 - log(abs($value));
} elseif ($value > 0.0) {
$value = log($value);
}
}
unset($value);
$this->_leastSquareFit($yValues, $xValues, $const);
} // function _logarithmic_regression()
function __construct($yValues, $xValues=array(), $const=True) {
if (parent::__construct($yValues, $xValues) !== False) {
$this->_logarithmic_regression($yValues, $xValues, $const);
}
} // function __construct()
} // class logarithmicBestFit

Source for file logarithmicBestFitClass.php