<?php
/**
 * This source file is part of the open source project
 * ExpressionEngine (https://expressionengine.com)
 *
 * @link      https://expressionengine.com/
 * @copyright Copyright (c) 2003-2022, Packet Tide, LLC (https://www.packettide.com)
 * @license   https://expressionengine.com/license Licensed under Apache License, Version 2.0
 */

namespace ExpressionEngine\Addons\Spam\Library;

/**
 * Spam Expectation
 */
class Expectation
{
    public $samples = array();
    public $count = 0;
    public $mean = 0;
    public $variance = 0;

    /**
     * Load the initial data and set the current mean/variance
     *
     * @param array An array of floats
     * @access public
     * @return void
     */
    public function __construct($samples)
    {
        $this->samples = $samples;
        $this->count = count($samples);
        $this->mean = $this->mean();
        $this->variance = $this->variance();
    }

    /**
     * Calculates and returns the sample mean
     *
     * @access public
     * @return Return the sample mean.
     */
    public function mean()
    {
        return array_sum($this->samples) / $this->count;
    }

    /**
     * Calculates and returns the variance
     * Note: sqrt(variance) == std deviation
     *
     * @access public
     * @return Return the sample variance.
     */
    public function variance()
    {
        $sum = 0;
        foreach ($this->samples as $sample) {
            $sum += pow($sample - $this->mean, 2);
        }

        return sqrt($sum / $this->count);
    }
}

// EOF
