Group rows in a collection by specified columns to build a 3d structure

Question

I need to group data from a 2d Laravel query result to form a 3d structure.

In Laravel, my data from ->get()->toArray() result is:

[
    ['ts' => 1234, 'a' => 3, 'b' => 2],
    ['ts' => 1244, 'a' => 2, 'b' => 6],
    ['ts' => 1254, 'a' => 8, 'b' => 3],
]

Is there any way that I am able to transform the data to as such:

[
    ['column' => 'a', 'values' => [[1234, 3], [1244, 2], [1254, 8]],
    ['column' => 'b', 'values' => [[1234, 2], [1244, 6], [1254, 3]],
]

I just wish to know if there's any best / efficient way to render the transformation as described above. Avoid re looping again as data is already available, it can be thought as a data formatting question. Also, I do not wish to use additional array if possible.

Things that I've already looked includes ->get()->map(function()), however this is sequential and I am not able to get values in 2D array as a result.

Answer 1

You'll want to map over your items and return the ts value, as well as the value for each column, respectively:

$items = Model::all();

$result = [
    [
        'column' => 'a',
        'values' => $items->map(function ($item) {
            return [$item->ts, $item->a];
        })
    ],
    [
        'column' => 'b',
        'values' => $items->map(function ($item) {
            return [$item->ts, $item->b];
        })
    ],
];

---

If you want to combine the logic for both columns, create a collection of column names, and map over those:

$items = Model::all();

$result = collect(['a', 'b'])->map(function ($column) use ($items) {
    $values = $items->map(function ($item) use ($column) {
        return [$item->ts, $item->{$column}];
    });

    return compact('column', 'values');
});