Keep only the three highest values in array of array in php-CodePudding

I have an array of 83 arrays (an array that I have a chunk in 83). I'm trying to keep only the three highest values of each array. All the numbers in each array are included between -1 and 1. There is necessarily a 1 in each array that I don't want to count in my three highest values.

        Array
    (
        [0] => Array
            (
                [1] => 0.5278533158407
                [2] => 0.4080014506744
                [3] => 0.5086879008467
                [5] => 0.3950042642736
                [6] => 1
        [1] => Array
            (
                [1] => 1
                [2] => 0.52873390443395
                [3] => 0.52518076782133
                [4] => 0.52983621494599
                [5] => 0.54392829322042
                [6] => 0.53636363636364

Etc...

I'm trying the below code but it doesn't work.

for ($i = 0; $i < sizeof($list_chunk); $i  ) {
        arsort($list_chunk[$i]);
        }
        
for ($i = 0; $i < sizeof($list_chunk); $i  ) {
        array_slice($list_chunk[$i],1,3,true);
        }
        
   
print("<pre>");
print_r($list_chunk);
print("</pre>");

Someone could help me? Thanks a lot

CodePudding user response：

Your code seems to be almost correct. You are sorting the arrays in descending order, but you are not storing the result of array_slice in any variable. As a result, the changes made by array_slice are not being saved.

Here is how you can fix the issue:

// Sort the arrays in descending order
for ($i = 0; $i < sizeof($list_chunk); $i  ) {
    arsort($list_chunk[$i]);
}

// Keep only the first three elements of each array
for ($i = 0; $i < sizeof($list_chunk); $i  ) {
    $list_chunk[$i] = array_slice($list_chunk[$i], 1, 3, true);
}

print("<pre>");
print_r($list_chunk);
print("</pre>");

Here, we are assigning the result of array_slice to the same variable. This will save the changes made by array_slice and you should get the desired output.

Alternatively, you can also use the array_splice function to achieve the same result. Here is how you can use it:

// Sort the arrays in descending order
for ($i = 0; $i < sizeof($list_chunk); $i  ) {
    arsort($list_chunk[$i]);
}

// Keep only the first three elements of each array
for ($i = 0; $i < sizeof($list_chunk); $i  ) {
    array_splice($list_chunk[$i], 3);
}

print("<pre>");
print_r($list_chunk);
print("</pre>");

This will have the same effect as array_slice, but you don't have to specify the start and end indexes explicitly. You just have to specify the number of elements to keep, and array_splice will remove all the elements after that.

CodePudding user response：

This solution uses a foreach loop with a reference to the subarray. The subarray is sorted in descending order of size. The first to third elements are extracted. If the first element is 1, then 3 elements are extracted from the 2 element onwards.

foreach($array as &$arr){
  rsort($arr);
  $start = $arr[0] == 1 ? 1 : 0;
  $arr = array_slice($arr,$start,3);
}

Result:

array (
  0 => 
  array (
    0 => 0.5278533158407,
    1 => 0.5086879008467,
    2 => 0.4080014506744,
  ),
  1 => 
  array (
    0 => 0.54392829322042,
    1 => 0.53636363636364,
    2 => 0.52983621494599,
  ),
)

Full sample to try: https://3v4l.org/pUhic