将每第3行连接到上一个第3行

Question

I made an earlier post but did not formulate the issue correctly. Hence, a question that may look like a previous one, but isn't. Consider the following data.csv:

 "1", "2", "3", "4"
 "5", "6", "7", "8"
 "9","10","11","12"
"13","14","15","16"
"17","18","19","20"
"21","22","23","24"
"25","26","27","28"
"29","30","31","32"
"33","34","35","36"

In reality, the rows and columns are much longer, but the principle stays the same. The output should be as follows:

• 3 rows
• every 3rd row is concatenated to the previous 3rd one, so
• row 4 (1 + 3) and 7 (1 + 3 + 3) are concatenated to row 1
• row 5 (2 + 3) and 8 (2 + 3 + 3) are concatenated to row 2
• row 6 (3 + 3) and 9 (3 + 3 + 3) are concatenated to row 3

The output then would be an array:

array (
  [0] => 1,2,3,4,13,14,15,16,25,26,27,28
  [1] => 5,6,7,8,17,18,19,20,29,30,31,32
  [2] => 9,10,11,12,21,22,23,24,33,34,35,36
)

Thanks to @nickb I now have:

$path = "data.csv";
$newrow = 1; $row = 1;
if (($handle = fopen($path, "r")) !== FALSE) {
  while (($data = fgetcsv($handle, 1000, ",")) !== FALSE) {
    if( !isset( $newrows[$newrow])) $newrows[$newrow] = '';
    $newrows[$newrow] .= implode(",", $data);
    if ($row % 3 == 0) {
        $newrow++;
    } else {
        $newrows[$newrow] .= ',';
    }
    $row++;
  }
}

print_r($newrows);

But this concatenated "all 3 consecutive" rows to eacht other, instead of "every third row". Who can tell me how to accomplish concatenating every 3rd row? I tried this but it concatenates in a weird way:

$path = "data.csv";
$row = 1;
if (($handle = fopen($path, "r")) !== FALSE) {
  while (($data = fgetcsv($handle, 1000, ",")) !== FALSE) {
    for ($i = 1; $i <= 3; $i++) {
      if ($row % $i == 0) $newrows[$i] .= implode(",", $data);
    }
    $row++;
  }
}

print_r($newrows);

Output:

Array (
    [1] => 1,2,3,45,6,7,89,10,11,1213,14,15,1617,18,19,2021,22,23,2425,26,27,2829,30,31,3233,34,35,36
    [2] => 5,6,7,813,14,15,1621,22,23,2429,30,31,32
    [3] => 9,10,11,1221,22,23,2433,34,35,36
)

edit In reality, the csv is much larger and I need every 147th row to be concatenated to the previous 147th row, but the principle is the same I guess.

Answer 1

EDIT: what you can do instead (and what is actually the smarter solution, shown here in Java) is:

String[] newarray = new String[147];
for(int i = 0; i < yourarray.length; i++){
    newarray[i%147].concat(yourarray[i]);
}

Replace String[] with whatever array type you need, and the concat() method with whatever method you use to concatenate arrays. The gist of the code is that you need some way to map the element in the original array at index 147n+C (for some non-negative integer n, and some integer C < 147) to the element in the new array at index C, which is essentially the purpose of modular arithmetic.

Answer 2

Your general logic should be:

• Take a row, which is the n'th row
• Take x equal to the floor of n/3
• Append row n's contents to the output row x

My PHP's too rusty to write the exact code to do that, but what you've got certainly won't do that.