Rank array values with possible duplicate values - php

Question

I am trying to rank an array of values and maintain the order in the original array.
So for example:
(6,4,7,12,7) should return (2,1,3,4,3)
(12,17,5,27,5) should return (2,3,1,4,1)
(1,1,4,6) should return (1,1,2,3)
In each case the returned array has the rank of the corresponding element in the original array, and duplicate values will have the same rank.
$values = array(12,17,5,27,5);
$sorted_values = $values;
sort($sorted_values);
foreach ($values as $key => $value) {
foreach ($sorted_values as $sorted_key => $sorted_value) {
if ($value == $sorted_value) {
$rank_key = $sorted_key;
break;
}
}
echo $value . ' has rank: ' . $rank_key + 1 . '<br>';
}

Answer 1

A simple way would be to first rank the unique values (using array_unique() followed by sort()), then translate the original list by this newly rank list (more comments in the code)...
$source = [12,17,5,27,5];
$output = [];
// Copy to work array unique values
$rank = array_unique($source);
// Sort it to produce ranking order
sort($rank);
// Make the number the key with the order as the value
$rank = array_flip($rank);
// Translate the values using $rank
foreach ( $source as $element ) {
$output[] = $rank[$element]+1;
}
print_r($output);
gives...
Array
(
[0] => 2
[1] => 3
[2] => 1
[3] => 4
[4] => 1
)

Answer 2

Clone your array, sort the clone by values, while keeping the key associations.
Loop over the clone, and in classical “control break” fashion, compare the value of the current item to that of the previous one. Increase the rank by one, if they differ. Set that rank as new value under that key.
Sort the clone by keys.
$data = [12,17,5,27,5];
$clone = $data;
asort($clone);
$rank = 0;
$previous_value = null; // something that doesn't ever occur in your array values
foreach($clone as $key => $value) {
if($value !== $previous_value) {
$rank++;
}
$clone[$key] = $rank;
$previous_value = $value;
}
ksort($clone);
var_dump($data, $clone);

Answer 3

you need to sort your array
This may close to your answer:
<?php
$my_array=array(12,17,5,27,5);
$ordered_values = $my_array;
$rank=array();
rsort($ordered_values);
foreach ($ordered_values as $key => $value) {
foreach ($ordered_values as $ordered_key => $ordered_value) {
if ($value === $ordered_value) {
$key = $ordered_key;
break;
}
}
$rank[$value]=((int) $key + 1) ;
}
foreach($my_array as $key => $value)
{
echo $value.':'.$rank[$value].'<br>';
}
?>

Answer 4

function rankDuplicateArray(array $array): array
{
$copy = array_unique($array);
sort($copy);
$flipArray = array_flip($copy);
return array_map(function($v) use ($flipArray) {
return $flipArray[$v] + 1;
}, $array);
}