Group and merge array row data based on one column

Question

I have an array a bit like:


Array (    
        [1] => Array
            (
                [1] => 21
                [2] => 3
                [0] => Analyst
            )    
        [2] => Array
            (
                [1] => 47
                [2] => 8
                [0] => Catalysis
            )

        [3] => Array
            (
                [1] => 1
                [2] => 0
                [0] => Biomaterials 
            )

        [4] => Array
            (
                [3] => 12
                [4] => 2
                [0] => Analyst
            )

       [5] => Array
            (
                [5] => 12
                [6] => 2
                [0] => Analyst
            )
...

However I would like to renumber those entries with the same [0] value so that I end up with


       [1] => Array
            (
                [1] => 21
                [2] => 3
                [3] => 12
                [4] => 2
                [5] => 12
                [6] => 2
                [0] => Analyst
            )

So far I've tried getting the [0] values out of the $results array by putting them in their own array and saying if you're already there then add [3] and [4] to where [1] and [2] are in a new array but it's not working.

$final = array();
$jArray = array();

foreach($results as $key => $result) {
  if(!in_array($result[0],$jArray) && !empty($result[0])) {
    $jArray[$i] = $result[0];
    $i++;
  }
}



for($x = 0; $x < count($results); $x++) { 
      $k = array_search($results[$x][0],$jArray);
    if(!isset($results[$x][1])) 
      $final[$k][1] = $results[$x][1];
    if(!isset($results[$x][2])) 
      $final[$k][2] = $results[$x][2];    
    if(!isset($results[$x][3])) 
      $final[$k][3] = $results[$x][3];
   if(!isset($results[$x][4])) 
      $final[$k][4] = $results[$x][4];
    if(!isset($results[$x][5]))     
      $final[$k][5] = $results[$x][5];
    if(!isset($results[$x][6]))     
      $final[$k][6] = $results[$x][6];
}

Any simpler ways of doing this?

Just put a second loop inside the loop.

sybear
– sybear

2014-04-16 11:39:34 +00:00
Commented Apr 16, 2014 at 11:39 — sybear
– sybear, Commented Apr 16, 2014 at 11:39

Shankar Narayana Damodaran · Accepted Answer · 2014-04-16 16:31:43Z

1

You can do this way...

$new_arr=array();
$arkeys = array_unique(array_map(function ($v){ return $v[0];},$arr));
foreach($arr as $k=>$arr1)
{
            $new_arr[$arr1[0]][]=array_slice($arr1,0,count($arr1)-1);
}

foreach($arkeys as $v)
{
$new_arr[$v] = call_user_func_array('array_merge', $new_arr[$v]);
}
print_r($new_arr);

OUTPUT :

Array
(
    [Analyst] => Array
        (
            [0] => 21
            [1] => 3
            [2] => 12
            [3] => 2
            [4] => 12
            [5] => 2
        )

    [Catalysis] => Array
        (
            [0] => 47
            [1] => 8
        )

    [Biomaterials] => Array
        (
            [0] => 1
            [1] => 0
        )

)

Working Demo

edited Apr 16, 2014 at 16:31

answered Apr 16, 2014 at 12:55

Shankar Narayana Damodaran

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1 Comment

ian Over a year ago

Nice, but I have 38 different "subjects" that may change so I would like something more elegant that a big switch statement

xdazz · Accepted Answer · 2014-04-17 02:24:43Z

1

If you just want to group by the first element of the sub array, a single loop is enough:

$result = array();

foreach ($array as $sub_arr) {
  $key = $sub_arr[0];
  unset($sub_arr[0]);
  if (!isset($result[$key])) {
    $result[$key] = array();
  }
  $result[$key] += $sub_arr;
}

answered Apr 17, 2014 at 2:24

xdazz

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Comments

KNaito · Accepted Answer · 2014-04-17 02:13:35Z

-1

Here

$final = array();

foreach($results as $key => $result) {
  if (!in_array($result[0], array_keys( $final ) ) && !empty($result[0])) {
    $final[$result[0]] = array( $result[0] );
  }
  foreach($result as $k => $v) {
    if ($k != 0 && isset($v)) {
      $final[$result[0]][$k] = $v;
    }
  } 
}

edited Apr 17, 2014 at 2:13

answered Apr 16, 2014 at 11:54

KNaito

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4 Comments

ian Over a year ago

I'm afraid it doesn't work: I get [] => [Analyst] => Array ( [0] => Analyst [1] => 21 [2] => 3 [3] => 4 [4] => 1 [5] => 42 [6] => 3 [7] => [8] => [9] => 4 [10] => 0 ) [Biomaterials] => Array ( [0] => Biomaterials [1] => 1 [2] => 0 [3] => [4] => [5] => [6] =>

ian Over a year ago

i.e. I dont know why 9 and 10 are filled in the first one and only 1 and 2 are filled in subsequently

KNaito Over a year ago

Sorry, I have misunderstood. Now I modified my codes.

mickmackusa Over a year ago

in_array($result[0], array_keys()) is definitely not an efficient way to check if a key exists in an array.

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