How to divide values in one array by values in another

PHP
1

I am trying to figure out how to divide the values in one associative array with the values in another, and put the results into a third associative array. The two starting arrays have the same key values: e.g…

$bus_type_totals = array('HO' => 15357, 'GH' => 3564, 'BB' => 62475, 'SC' => 247575, 'CP' => 3145, 'HS' => 7322, 'CS' => 2466);
$bus_type_sample = array('HO' => 234, 'GH' => 135, 'BB' => 236, 'SC' => 754, 'CP' => 54, 'HS' => 865, 'CS' => 432);

and the results array needs the same keys too.

So how to divide the ‘HO’ value in the first array by the ‘HO’ value in the second, and so on ?

I can’t help feeling it should be very easy, but I want to avoid citing the keys themselves (they may change, but will always be the same in both arrays). It would be easier if the keys were numerical, as I could use a ‘for’ loop, but I need the keys in the result.

Perhaps I can bend array_walk to the task, but I’m struggling. Any ideas, please ?

2

I thought this was an interesting exercise, so here’s what I came up with:

<?php

$bus_type_totals = array('HO' => 15357, 'GH' => 3564, 'BB' => 62475, 'SC' => 247575, 'CP' => 3145, 'HS' => 7322, 'CS' => 2466);
$bus_type_sample = array('HO' => 234, 'GH' => 135, 'BB' => 236, 'SC' => 754, 'CP' => 54, 'HS' => 865, 'CS' => 432); 

/* check for data integrity before performing calculations */
if(keys_are_equal($bus_type_totals,$bus_type_sample)){
    
    $the_calculated_value = -1;
    
    $keys = array_keys($bus_type_totals); /* returns an array of the keys listed in the array */
    foreach($keys as $key ){
        $the_calculated_value=$bus_type_totals[$key]/$bus_type_sample[$key]; /* I'm not sure which way you're actually dividing the values, so feel free to change as necessary */
        
        /* do something with the calculated value here */
        echo $key.': '.$the_calculated_value;
        echo '<br>';
        /* maybe save the resulting value in an array for later use, or use it for something else here */
    }
}
else {
    echo 'error: array mismatch';
}


/* this function verifies that the two arrays have the same keys */
function keys_are_equal($array1, $array2) {
  return !array_diff_key($array1, $array2) && !array_diff_key($array2, $array1);
}

?>
3

Uses Lambda Functions.


$out = array_map(function ($a,$b) { return $a / $b; },$bus_type_totals,$bus_type_sample);

EDIT: This will cause the loss of key values, though, and doesnt check that the arrays align.

4

Thank you, Force Flow. Leaving out the integrity check, I now have:

$keys = array_keys($bus_type_totals);
foreach ($keys as $key) {
	$bus_type_average[$key] = $bus_type_totals[$key]/$bus_type_sample[$key];
}

That works for me, though I’ll need to deal with potential divide by zero erors. It’s good to have the check for parity too. Thanks again.

5

Just use an if-statement to check for that.

<?php

$bus_type_totals = array('HO' => 15357, 'GH' => 3564, 'BB' => 62475, 'SC' => 247575, 'CP' => 3145, 'HS' => 7322, 'CS' => 2466);
$bus_type_sample = array('HO' => 234, 'GH' => 135, 'BB' => 236, 'SC' => 754, 'CP' => 54, 'HS' => 865, 'CS' => 432); 


$the_calculated_value = -1;
    
$keys = array_keys($bus_type_totals); /* returns an array of the keys listed in the array */
foreach($keys as $key ){
    $the_calculated_value = -1; //set a default value for each loop so you can identify when you don't actually get a result
        
    if($bus_type_sample[$key]>0){ /* if the divisor is greater than zero, go ahead with the calculation */
        $the_calculated_value=$bus_type_totals[$key]/$bus_type_sample[$key]; 
        /* your code to handle the result */
    }
    else{
        echo $key.' is zero. Calculation cannot be processed.';
    }

}


?>
6

Thanks again.