phparraysmultidimensional-arrayaveragearray-column

Calculate the average of each column in a 2d array

I need to calculate the average value for each column of data in an array of associative arrays. The result should be a flat, associative array of averages.

Sample array:

$array = [
  [
    "a" => 0.333,
    "b" => 0.730,
    "c" => 0.393
  ],
  [
    "a" => 0.323,
    "b" => 0.454,
    "c" => 0.987
  ],
  [
    "a" => 0.753,
    "b" => 0.983,
    "c" => 0.123
  ]
];

I am looking for a simpler way of processing all the array elements and producing a single array which has a mean value (average) of all the corresponding values.

My current code works, but I'm hoping for a more elegant approach.

$a = []; // Store all a values
$b = []; // Store all b values
$c = []; // Store all c values

for ( $i = 0; $i < count( $array ); $i ++ ) {
    // For each array, store each value in it's corresponsing array
    // Using variable variables to make it easy
    foreach ( $array[ $i ] AS $key => $val ) {
        $k    = $key;
        $$k[] = $val;
    };
}

// Create single array with average of all
$fa = array(
    'a' => array_sum($a) / count($a),
    'b' => array_sum($b) / count($b),
    'c' => array_sum($c) / count($c)
);

The desired result:

[
    'a' => 0.4696666666666667,
    'b' => 0.7223333333333333,
    'c' => 0.501,
]
Solution

  • Assuming each sub-array has the same keys:

    foreach(array_keys($array[0]) as $key) {
    $result[$key] = array_sum($tmp = array_column($array, $key))/count($tmp);
}