转置 csv 文件数据

Question

我需要帮助将 keys 分配给 PHP 中的 array。

我的代码是：

//First I make an array of a csv file
$file="C:\path-to-csv\file.csv";
$csv= file_get_contents($file);
$array = array_map("str_getcsv", explode("\n", $csv));

array:

//echo json_encode($array);
["0","20150717","2:57:00","1437145020","1.56084","1.56096","1.56084","1.56094","5"],
["1","20150717","2:56:00","1437144960","1.56071","1.56089","1.56071","1.56089","9"],
["2","20150717","2:55:00","1437144900","1.5607","1.5607","1.56064","1.56064","2"], //continue

根据 $array 的结果，我需要将特定的 key 分配给特定的列并创建一个新的 array“$newArray”。因此，结果如下所示：

//$newArray should print:
"ID" :  [0, 1, 2],                      //I would like delete this value
"n"  :  [20150717, 20150717, 20150717], //I would like delete this value
"d"  :  [2:57:00, 2:56:00, 2:55:00],    //I would like delete this value
"t"  :  [1437145020, 1437144960, 1437144900], //column 4
"o"  :  [1.56084, 1.56071, 1.5607],     //column 5
"h"  :  [1.56096, 1.56089, 1.5607],     // column 6
"l"  :  [1.56084, 1.56071, 1.56064],    // column 7
"c"  :  [1.56094, 1.56089, 1.56064],    //column 8
"v"  :  [5, 9, 2]                      //column 9

我尝试通过循环和一些函数（例如 array_fill_keys 和 array_column 来做到这一点，但我得不到想要的结果。如果你能帮助我，我将不胜感激，$array 有超过 1000 个条目，因此优化代码执行速度非常重要，老实说超出了我的知识范围，我在 Google 中没有看到任何东西] 帮我完成这个。谢谢你的时间，对不起我的语法。

Answer 1

EDIT 差不多，这个解决方案可以用 <5.5，当 array_column 不可用时。

对于一个 foreach 循环来说，超过 1000 个条目似乎并不多。

$keys = array('t','o','h','l','c','v');    
$newArray = array();

foreach ($array as $j) {
    $r = array_slice($j, 3);
    foreach ($r as $i => $v) $newArray[$keys[$i]][] = $v*1; 
}

Json 编码结果将是

"t":[1437144900,1437144900,1437145020],
"o":[1.5607,1.5607,1.56084],
"h":[1.5607,1.5607,1.56096],
"l":[1.56064,1.56064,1.56084],
"c":[1.56064,1.56064,1.56094],
"v":[2,2,5]

运行一个包含 10.000 个条目的数组占用了

0.020426

您可以在 PhpFiddle 上测试自己。

Answer 2

如果您使用的是 PHP 5.5，则可以使用 array_column:

$newArray = array(
    't' => array_column($array, 3),
    'o' => array_column($array, 4),
    'h' => array_column($array, 5),
    ...
);

如果您使用的是旧版 PHP，您可以在 Is there a function to extract a 'column' from an array in PHP?

找到它的 PHP 实现

转置 csv 文件数据

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