class.ilStatistics.php

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<?php
/*
        +-----------------------------------------------------------------------------+
        | ILIAS open source                                                           |
        +-----------------------------------------------------------------------------+
        | Copyright (c) 1998-2001 ILIAS open source, University of Cologne            |
        |                                                                             |
        | This program is free software; you can redistribute it and/or               |
        | modify it under the terms of the GNU General Public License                 |
        | as published by the Free Software Foundation; either version 2              |
        | of the License, or (at your option) any later version.                      |
        |                                                                             |
        | This program 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 General Public License for more details.                                |
        |                                                                             |
        | You should have received a copy of the GNU General Public License           |
        | along with this program; if not, write to the Free Software                 |
        | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA. |
        +-----------------------------------------------------------------------------+
*/

        define("NAN_HANDLING_REMOVE", 0);
        define("NAN_HANDLING_ZERO", 1);

class ilStatistics
{
        var $nan_handling;
        
        var $stat_data;
        
        function ilStatistics($nan_handling = NAN_HANDLING_REMOVE)
        {
                $this->nan_handling = $nan_handling;
                $this->stat_data = array();
        }
        
        function setNANHandling($nan_handling = NAN_HANDLING_REMOVE)
        {
                $this->nan_handling = $nan_handling;
        }
        
        function getNANHandling()
        {
                return $this->nan_handling;
        }
        
        function setData($stat_data)
        {
                $this->stat_data = array_values($stat_data);
                $this->validate();
        }
        
        function getData()
        {
                return $this->stat_data;
        }

        function min() {
                if (count($this->stat_data))
                {
                        $min = min($this->stat_data);
                }
                else
                {
                        $min = false;
                }
                return $min;
        }

        function max() {
                if (count($this->stat_data))
                {
                        $max = max($this->stat_data);
                }
                else
                {
                        $max = false;
                }
                return $max;
        }

        function count() {
                return count($this->stat_data);
        }

        function sum_n($n) {
                $sum_n = false;
                if (count($this->stat_data))
                {
                        $sum_n = 0;
                        foreach ($this->stat_data as $value)
                        {
                                $sum_n += pow((double)$value, (double)$n);
                        }
                }
                return $sum_n;
        }

        function sum() {
                return $this->sum_n(1);
        }


        function sum2() {
                return $this->sum_n(2);
        }
        
        function product_n($n) {
                $prod_n = false;
                if (count($this->stat_data))
                {
                        if ($this->min() === 0)
                        {
                                return 0.0;
                        }
                        $prod_n = 1.0;
                        foreach ($this->stat_data as $value)
                        {
                                $prod_n *= pow((double)$value, (double)$n);
                        }
                }
                return $prod_n;
        }

        function product($n) {
                return $this->product_n(1);
        }

        function arithmetic_mean() {
                $sum = $this->sum();
                if ($sum === false)
                {
                        return false;
                }
                $count = $this->count();
                if ($count == 0)
                {
                        return false;
                }
                return (double)($sum/$count);
        }

        function geometric_mean() {
                $prod = $this->product();
                if (($prod === false) or ($prod === 0))
                {
                        return false;
                }
                $count = $this->count();
                if ($count == 0)
                {
                        return false;
                }
                return pow((double)$prod, (double)(1/$count));
        }

        function harmonic_mean() {
                $min = $this->min();
                if (($min === false) or ($min === 0))
                {
                        return false;
                }
                $count = $this->count();
                if ($count == 0)
                {
                        return false;
                }
                $sum = 0;
                foreach ($this->stat_data as $value)
                {
                        $sum += 1/$value;
                }
                return $count/$sum;
        }

        function median() {
                $median = false;
                if (count($this->stat_data))
                {
                        $median = 0;
                        $count = $this->count();
                        if ((count($this->stat_data) % 2) == 0)
                        {
                                $median = ($this->stat_data[($count / 2) - 1] + $this->stat_data[($count / 2)]) / 2;
                        }
                        else
                        {
                                $median = $this->stat_data[(($count + 1) / 2) - 1];
                        }
                }
                return $median;
        }
        
        function rank($value)
        {
                if (!is_numeric($value))
                {
                        return false;
                }
                $rank = array_search($value, $this->stat_data);
                if ($rank !== FALSE)
                {
                        $rank = $this->count() - $rank;
                }
                return $rank;
        }
        
        function rank_median()
        {
                $count = $this->count();
                if ($count == 0)
                {
                        return false;
                }
                
                if (($count % 2) == 0)
                {
                        $rank_median = ($count + 1) / 2;
                }
                else
                {
                        $rank_median = ($count + 1) / 2;
                }
                return $rank_median;
        }
        
        function quantile($n) {
                $count = $this->count();
                if ($count == 0)
                {
                        return false;
                }
                $nprod = ($n/100)*$count;
                if (intval($nprod) == $nprod)
                {
                        $k = $nprod;
                        if ($k == 0)
                        {
                                return $this->stat_data[$k];
                        }
                        else if ($k == $count)
                        {
                                return $this->stat_data[$k-1];
                        }
                        else
                        {
                                return ($this->stat_data[$k-1] + $this->stat_data[$k])/2;
                        }
                }
                else
                {
                        $k = ceil($nprod);
                        return $this->stat_data[$k-1];
                }
        }
        
        function validate()
        {
                $result = true;
                foreach ($this->stat_data as $key => $value)
                {
                        if (!is_numeric($value)) {
                                switch ($this->nan_handling) {
                                        case NAN_HANDLING_REMOVE:
                                                unset($this->stat_data[$key]);
                                                break;
                                        case NAN_HANDLING_ZERO:
                                                $this->stat_data[$key] = 0;
                                                break;
                                        default:
                                                $result = false;
                                }
                        }
                }
                sort($this->stat_data);
                return $result;
        }
}

?>