Question

php 二维数组分组求平均值放入一个新数组

array(
array('weight' => '55','time'=>'2014-02-03'),
array('weight' => '75','time'=>'2014-02-03'),
array('weight' => '65','time'=>'2014-02-03'),
array('weight' => '72','time'=>'2014-04-12'),
array('weight' => '25','time'=>'2014-04-12')
),
求在同一个time 下weight的平均值 然后组成一个新数组

Answer 1

<?php
$arr1 = array(
    array('weight' => '55','time'=>'2014-02-03'),
    array('weight' => '75','time'=>'2014-02-03'),
    array('weight' => '65','time'=>'2014-02-03'),
    array('weight' => '72','time'=>'2014-04-12'),
    array('weight' => '25','time'=>'2014-04-12')
);

$arr2 = array();
foreach ($arr1 as $value) {
    $arr2[$value['time']][] = $value['weight'];
}

$arr3 = array();
foreach($arr2 as $key => $value){
    $arr3[$key] = array_sum($value) / count($value);
}

var_dump($arr3);

?>