How to calculate average from multiple array in php?

Question

I have some array value returns from the database like

$rate =
    ["1.55","1","1","1"]
    ["2.55","2.55","2.55","2.55"]
    ["1","1","1","1"]
    ["1.2","1.21","1.2","1.2"]

My Actual DB Value

array(4) {
  [0]=>
  array(1) {
    ["rate"]=>
    string(20) "["1.55","1","1","1"]"
  }
  [1]=>
  array(1) {
    ["rate"]=>
    string(29) "["2.55","2.55","2.55","2.55"]"
  }
  [2]=>
  array(1) {
    ["rate"]=>
    string(17) "["1","1","1","1"]"
  }
  [3]=>
  array(1) {
    ["rate"]=>
    string(29) "["1.55","2.55","3.55","4.56"]"
  }
}

So the calculation is

1.55+2.55+1+1.2 =6.3/4 =1.57
1+2.55+1+1.21 =5.76/4 =1.44
1+2.55+1+1.2 =5.75/4 =1.43
1+2.55+1+1.2 =5.75/4 =1.43

How to get an average from those values and the result is something like

["1.57","1.44","1.43","1.43"]

What I have tried so far

foreach($dibor_data as $key=>$value){
    if(array_key_exists($key,$sum)){
        $repeat[$key] = $repeat[$key]+1;
        $sum[$key] = $sum[$key] + json_decode($value['rate']);
    }
}

Where are you stuck? Iterating over the arrays? Addition? Division? — brombeer, Oct 24 '22 at 08:55
Implementation of my answer on the dupe target using your updated "snowflake" data structure: https://3v4l.org/UOVtH — mickmackusa, Oct 24 '22 at 20:03

score 1 · Accepted Answer · edited Oct 25 '22 at 05:18

Assuming you have an array of arrays (it's not clear from your code that that is so) then you can use array_column() to step across the columns, and array_sum() and count() to calculate the averages.

<?php

$rate = [
    ["1.55","1","1","1"],
    ["2.55","2.55","2.55","2.55"],
    ["1","1","1","1"],
    ["1.2","1.21","1.2","1.2"]
];

$results =[];

// Count the columns in the first row
for ($i = 0; $i<sizeof ($rate[0]); $i++) {

  // Extract each column in turn
  $col = array_column($rate, $i);

  // Calculate and store the averages

  $results[]= array_sum($col)/count($col);

}
var_dump($results);

Output

array(4) {
  [0]=>
  float(1.575)
  [1]=>
  float(1.44)
  [2]=>
  float(1.4375)
  [3]=>
  float(1.4375)
}

Update: Since the OP has now posted some real data, it needs a little preprocessing before this code will work. The original data is stored in a database as JSON strings, so these need to be extracted and decoded. array_map() does this nicely.

// Array with new database data
$dbData = [
    ["rate"=>'["1.55","1","1","1"]'],
    ["rate"=>'["2.55","2.55","2.55","2.55"]'],
    ["rate"=>'["1","1","1","1"]'],
    ["rate"=>'["1.55","2.55","3.55","4.56"]']
];

// array_map calls json_decode() on the 'rate' element of each array element

Method 1:

$rate = array_map(function($a){
    return json_decode($a['rate']);
},$dbData);

// code from here on as above.

Method 2:

foreach ($dbData as $key => $ev){
    $rate_data[] = $ev['rate'];
}

$rate_array = implode(', ',$rate_data);
$json_rate = '[ '. $rate_array .' ]';  //Json string

//convert JSON string to array
$rate = json_decode($json_rate, TRUE);

See: https://3v4l.org/X7haS

Note: It's rarely a good idea to store data in a database as JSON strings. If you'd taken the trouble to separate out the values in the JSON strings and store them in separate columns all this malarkey could be avoided by asking the database to return the averages directly.

Thanks for the solution. I have solved this in another way I have added as method 2. I saved it as JSON due to value is dynamic and has no limit of columns. I can also save those values as serialized data but JSON is faster I think — Firefog, Oct 25 '22 at 05:18

How to calculate average from multiple array in php?

1 Answers1