Transpose csv file data

Question

I need help to assign keys to an array in PHP.

My code is:

//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));

The 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

From the result of $array, I need to assign a specific key to a specific column and create a new array "$newArray". So, the result looks like this:

//$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

I have tried to do it through loops and some functions such as array_fill_keys and array_column but I can not get the desired result. I would greatly appreciate if you can help me, the $array has more than 1000 entries so it would be really important to optimize the code execution speed, and honestly exceeds my knowledge and I have not seen anything in Google to help me accomplish this. Thanks for your time, sorry for my grammar.

One way to optimise would be to use a loop and `fgetcsv()` instead of `$csv= file_get_contents($file);`.... because you're still demanding a large chunk of memory for 1000 entries-worth of `$csv` — Mark Baker, Jul 17 '15 at 22:07
See this question, it might help I guess: http://stackoverflow.com/questions/797251/transposing-multidimensional-arrays-in-php — buff, Jul 17 '15 at 22:09
@buff Yes, I saw a few hours ago but I could not transfer it to my code, I'll keep reading ... Thanks anyway :)! — Max, Jul 17 '15 at 22:28

JungleZombie · Answer 1 · 2015-07-17T23:10:02.907

EDIT Pretty much, this solution can be used <5.5, when array_column is not available to you.

More than 1000 entries does not seem to be that much for a foreach loop.

$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 encoded result will be

"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]

Running an array containing 10.000 entries took

0.020426

You can test yourself on PhpFiddle.

score 0 · Accepted Answer · edited Aug 30 '21 at 06:46

0

If you're using PHP 5.5, you can make use of array_column:

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

If you're using an older PHP, you can find a PHP implementation of it at Is there a function to extract a 'column' from an array in PHP?

edited Aug 30 '21 at 06:46

mickmackusa

43,625
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answered Jul 17 '15 at 22:51

Barmar

741,623
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612

I choose this answer as best because it took `0.06900` and the answer of @JungleZombie took `0.12100 ` both work great so thank you very much for your help. – Max Jul 17 '15 at 23:12

Transpose csv file data

2 Answers2