TREND_LINEAR
TREND_LINEAR = 'Linear'
PHPExcel_trendClass
$_trendTypes : string[]
Names of the best-fit trend analysis methods
$_trendTypePolyOrders : string[]
Names of the best-fit trend polynomial orders
$_trendCache : \PHPExcel_Best_Fit[]
Cached results for each method when trying to identify which provides the best fit
<?php
/**
* PHPExcel
*
* Copyright (c) 2006 - 2014 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_Trend
* @copyright Copyright (c) 2006 - 2014 PHPExcel (http://www.codeplex.com/PHPExcel)
* @license http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt LGPL
* @version 1.8.0, 2014-03-02
*/
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';
/**
* PHPExcel_trendClass
*
* @category PHPExcel
* @package PHPExcel_Shared_Trend
* @copyright Copyright (c) 2006 - 2014 PHPExcel (http://www.codeplex.com/PHPExcel)
*/
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';
/**
* Names of the best-fit trend analysis methods
*
* @var string[]
**/
private static $_trendTypes = array( self::TREND_LINEAR,
self::TREND_LOGARITHMIC,
self::TREND_EXPONENTIAL,
self::TREND_POWER
);
/**
* Names of the best-fit trend polynomial orders
*
* @var string[]
**/
private static $_trendTypePolyOrders = array( self::TREND_POLYNOMIAL_2,
self::TREND_POLYNOMIAL_3,
self::TREND_POLYNOMIAL_4,
self::TREND_POLYNOMIAL_5,
self::TREND_POLYNOMIAL_6
);
/**
* Cached results for each method when trying to identify which provides the best fit
*
* @var PHPExcel_Best_Fit[]
**/
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