Sum each column of a 2d array

Question

I need a little help with summing up the columns in a two-dimensional array.

Eg Multidimensional array

Array
(
    [0] => Array
        (
            [0] => 30
            [1] => 5
            [2] => 6
            [3] => 7
            [4] => 8
            [5] => 9
            [6] => 2
            [7] => 5
        )

    [1] => Array
        (
            [0] => 50
            [1] => 4
            [2] => 8
            [3] => 4
            [4] => 4
            [5] => 6
            [6] => 9
            [7] => 2
        )
)

I want to have a result array that will hold the columnar sums of both rows.

Array
(
    [0] => 80
    [1] => 9
    [2] => 14
    [3] => 11
    [4] => 12
    [5] => 15
    [6] => 11
    [7] => 7
)

what you tried till now?

HaveNoDisplayName
– HaveNoDisplayName

2015-01-24 17:49:56 +00:00
Commented Jan 24, 2015 at 17:49 — HaveNoDisplayName
– HaveNoDisplayName, Commented Jan 24, 2015 at 17:49
Have you tried anyting? if so please post your code

NoLiver92
– NoLiver92

2015-01-24 17:52:10 +00:00
Commented Jan 24, 2015 at 17:52 — NoLiver92
– NoLiver92, Commented Jan 24, 2015 at 17:52

Rizier123 · Accepted Answer · 2015-01-24 18:16:14Z

3

This should work for you:

<?php

    $arr = array(
            array(30, 5, 6, 7, 8, 9, 2, 5), 
            array(50, 4, 8, 4, 4, 6, 9, 2)
        );

    $result = array();

    foreach($arr[0] as $k => $v)
        $result[$k] = array_sum(array_column($arr, $k));

    print_r($result);

?>

Output:

Array ( [0] => 80 [1] => 9 [2] => 14 [3] => 11 [4] => 12 [5] => 15 [6] => 11 [7] => 7 )

EDIT:

If your php version is under 5.4 you can use this simple workaround:

function arrayColumn(array $array, $column_key, $index_key=null){
    if(function_exists('array_column ')){
        return array_column($array, $column_key, $index_key);
    }
    $result = [];
    foreach($array as $arr){
        if(!is_array($arr)) continue;

        if(is_null($column_key)){
            $value = $arr;
        }else{
            $value = $arr[$column_key];
        }

        if(!is_null($index_key)){
            $key = $arr[$index_key];
            $result[$key] = $value;
        }else{
            $result[] = $value;
        }

    }

    return $result;
}

(Note that you have to use arrayColumn())

From the manual comments: http://php.net/manual/de/function.array-column.php#116301

edited Jan 24, 2015 at 18:16

answered Jan 24, 2015 at 17:56

Rizier123

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2 Comments

Pradeep Srivastava Over a year ago

Thanks Rizier but i am using php v 5.4 and it doesn't support array_column else it was a perfect answer Cheers!!!

acontell Over a year ago

I liked your first algorithm for its simplicity, don't like your workaround though. I've been benchmarking your algorithm and mine. It took mine 0.16s to get the result in an array of 100000 subarrays of 8 elements and it took 0.97s yours... It gets worse when the subarrays are bigger: array of 100000 subarrays of 20 elements: 0.45s mine, 2.77s yours

acontell · Accepted Answer · 2015-01-24 17:58:12Z

2

This should work for arrays like the one of your example ($arr is an array like the one in your example, I haven't defined it here for simplicity's sake):

$res = array();
foreach($arr as $value) {
    foreach($value as $key => $number) {
        (!isset($res[$key])) ?
            $res[$key] = $number :
            $res[$key] += $number;
    }
}

print_r($res);

answered Jan 24, 2015 at 17:58

acontell

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2 Comments

harrrrrrry Over a year ago

Look at @Rizier123's answer. It's more efficient.

acontell Over a year ago

@zairwolf indeed it's a great answer, sadly not very compatible. I use PHP 5.4 and here it doesn't work (requires PHP >=5.5)

mickmackusa · Accepted Answer · 2023-01-03 09:14:00Z

0

This answer is CERTAINLY not suitable with PHP5.4. The arrow function syntax became available as of PHP7.4.

Use the spread operator to unpack the input 2d array as separate row when fed to array_map(). This will send multiple values per column from each row. Using variadic data collection inside of the arrow function's argument signature ((...$col)) results in a single array variable containing all columnar values. Feed that array to array_sum() to get the desired result.

Code: (Demo)

$array = [
    [30, 5, 6, 7, 8, 9, 2, 5], 
    [50, 4, 8, 4, 4, 6, 9, 2]
];

var_export(
    array_map(
        fn(...$col) => array_sum($col),
        ...$array
    )
);

answered Jan 3, 2023 at 9:14

mickmackusa♦

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