Refactor code structure for improved readability and maintainability

themes/codebase4.0/grid-excel-php/lib/PHPExcel/Shared/trend/logarithmicBestFitClass.php

@@ -0,0 +1,82 @@
+<?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