Question

I have a collection of “answers” (multi-dimensional array) which is extracted from a database. I need to perform a calculation on each value so that I can show the results on a graph.

Here is some sample input:

$array = [
    'A1' => [1 => 1, 2 => 0, 3 => 0, 4 => 0, 5 => 0, 6 => 0, 7 => 0, 8 => 0, 9 => 0, 10 => 0],
    'A2' => [1 => 1, 2 => 1, 3 => 0, 4 => 0, 5 => 0, 6 => 0, 7 => 0, 8 => 0, 9 => 0, 10 => 0],
    'A3' => [1 => 0, 2 => 0, 3 => 0, 4 => 0, 5 => 0, 6 => 0, 7 => 0, 8 => 0, 9 => 0, 10 => 0]
];

I want to calculate a percentage value from the multidimensional array using this kind of logic:

[A1] => Array( ([1]*100/sum([1]+[1]+[1]), [2]*100/sum([2]+[2]+[2]),..... )
[A2] => Array( ([1]*100/sum([1]+[1]+[1]), [2]*100/sum([2]+[2]+[2]),..... )
[A3] => Array( ([3]*100/sum([1]+[1]+[1]), [2]*100/sum([2]+[2]+[2]),..... )

How can I do this?

My desired output:

[
  'A1' => [1 => 50, 2 => 0,   3 => 0, 4 => 0, 5 => 0, 6 => 0, 7 => 0, 8 => 0, 9 => 0, 10 => 0],
  'A2' => [1 => 50, 2 => 100, 3 => 0, 4 => 0, 5 => 0, 6 => 0, 7 => 0, 8 => 0, 9 => 0, 10 => 0],
  'A3' => [1 => 0,  2 => 0,   3 => 0, 4 => 0, 5 => 0, 6 => 0, 7 => 0, 8 => 0, 9 => 0, 10 => 0]
]

Answer 1

Ahh, I see what you’re trying to do now.

Try this

$totals = array();

// First get our totals.
foreach ($mainArray as $subKey => $subArray) {
    foreach ($subArray as $k => $v) {
        // Add the column to our total.
        $totals[$k] = isset($totals[$k]) ? $totals[$k] + $v : $v;
    }
}

$answers = array();
// Then build our answers.
foreach ($mainArray as $subKey => $subArray) {
    $answers[$subKey] = array();
    foreach ($subArray as $k => $v) {
        $answers[$subKey][$k] = ($v * 100) / $totals[$k];
    }
}

print_r($answers);