Calculating average value for array with PHP?

Question

My head is exploding with this. I can't seem to create a working solution.

I have a file in this format:

99895|35378|0.01
99895|813|-0.97
99895|771|0.29
442|833|-1.06
442|485|-0.61
442|367|-0.14
442|478|0.77
442|947|-0.07
7977|987|0.76
7977|819|0.37
7977|819|0.36
7977|653|1.16
7977|1653|1.15

I want to calculate average values from third column for each id from the first column.

This seems so easy but I can't get this to work. How do you get averages for any said id from first column?

EDIT:

Some sample code I've written before:

$file = file_get_contents("results.txt");


$file = explode("
", $file);

$howMany = count($file);

for($a = 0;$a<$howMany;$a++)
{

$row = explode("|", $file[$a]);
$id = $row[0];



$howManyAlready = count($bigTable[$id]);

$bigTable[$id][$howManyAlready] = $row[2];

}

I've added the code. So far it gets the results into an array ( with offset corresponding to its id ) But I am having trouble with how to get those results and calculate average for each id and then present it on the screen.

Please provide the code you wrote already, and solutions you are working on. And tell us what is wrong with your current code. — Thibault
– Thibault, Commented Dec 19, 2013 at 11:48
Are you values already in an array, or in a separate file you need to read ? — Theox
– Theox, Commented Dec 19, 2013 at 11:49
I've deleted it all as it was driving me mad. I was sitting 2 hours at this trivial problem. — user3010273
– user3010273, Commented Dec 19, 2013 at 11:49
@user3010273 Stackoverflow is about the code. Write the algorithm, then write some code, and we will help you if it doesn't work. Here are some functions that might help your : fgetcsv to read your file, array_sum and count to calculate the average for each id. — Thibault
– Thibault, Commented Dec 19, 2013 at 11:52

Shankar Narayana Damodaran · Accepted Answer · 2013-12-19 12:07:59Z

5

Something like this should definitely work..

<?php
$arr=array();
$arrv=array_filter(file('myfile.txt'),'strlen');
foreach($arrv as $v)
{
    array_push($arr,@array_pop(explode('|',$v)));
}
echo $avg = array_sum($arr)/count($arr);

answered Dec 19, 2013 at 12:07

Shankar Narayana Damodaran

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Comments

Theox · Accepted Answer · 2013-12-19 12:10:26Z

1

You can try doing this :

$file = file_get_contents("results.txt");
$file = explode("
", $file);

$valuesPerID = Array();

foreach($file as $row)
{

    $row_array = explode("|", $row);

    $id = $row_array[0];

    if(!array_key_exists($id, $valuesPerID))
    {
        $valuesPerID[$id] = Array();
    }

    $valuesPerID[$id][] = $row_array[2];

}

Now in the $valuesPerID array, you'll have all your ID as keys, and for each ID, all the values associated with the said ID. They you can easily calculate the average of these values !

edited Dec 19, 2013 at 12:10

answered Dec 19, 2013 at 11:55

Theox

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1 Comment

minipif Over a year ago

You should check the file function, that reads an entire file into an array, and takes care of the different possible line endings.

user1902830 · Accepted Answer · 2013-12-19 12:02:05Z

1

You can use array mapping to assign value and id. For example (assume that you have handled the text):

<?php
    $data = array("99895|35378|0.01",
        "99895|813|-0.97",
        "99895|771|0.29",
        "442|833|-1.06",
        "442|485|-0.61",
        "442|367|-0.14",
        "442|478|0.77",
        "442|947|-0.07",
        "7977|987|0.76",
        "7977|819|0.37",
        "7977|819|0.36",
        "7977|653|1.16",
        "7977|1653|1.15");

    $bucket = array();
    $count = array();
    foreach($data as $line) {
        list($id, $what_s_this, $number) = explode("|", $line);
        $count[$id]++;
        $bucket[$id]+= (float)$number;
    }

    foreach($bucket as $id => $sum) {
        echo "id:". $id. ", average". $sum / $count[$id]. "\n";
    }

answered Dec 19, 2013 at 12:02

user1902830

1 Comment

Albzi Over a year ago

Just tested, undefined offsets everywhere.

Anthony Sterling · Accepted Answer · 2013-12-19 12:08:41Z

1

This should put you on the right track.

<?php
$values = array();

foreach (file('file.txt') as $line) {
    list($id, $thingymabob, $value) = explode('|', $line);

    if ( ! array_key_exists($id, $values)) {
        $values[ $id ] = array();
    }

    array_push($values[ $id ], $value);
}

foreach ($values as $id => $value) {
    printf(
        "%d has an average of %f\n",
        $id,
        array_sum($value) / count($value)
    );
}

answered Dec 19, 2013 at 12:08

Anthony Sterling

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Comments

Albzi · Accepted Answer · 2013-12-19 12:11:01Z

1

Here some something I've just written.

In my example it takes it from a string.

<?php
$test1 = "";
$test2 = "";
$count1 = 0;
$count2 = 0;
$string = "99895|35378|0.01
99895|813|-0.97
99895|771|0.29
442|833|-1.06
442|485|-0.61
442|367|-0.14
442|478|0.77
442|947|-0.07
7977|987|0.76
7977|819|0.37
7977|819|0.36
7977|653|1.16
7977|1653|1.15";

$d = explode("\n", $string);
foreach ($d as $k => $v)
{
    $d2 = explode("|", $v);

    if ($d2[0] == '99895'){
        $count1++;
        $test1 += $d2[2];
    }
    if ($d2[0] == '442'){
        $count2++;
        $test2 += $d2[2];
    }
}

$result1 = $test1 / $count1;
$result2 = $test2 / $count2;

echo $result1. " <br> ". $result2;

I don't know how well this will work as I don't know if the values are set or not.

edited Dec 19, 2013 at 12:11

answered Dec 19, 2013 at 12:05

Albzi

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Comments

Ripa Saha · Accepted Answer · 2013-12-19 12:32:03Z

If You try below code

<?php
$file_content = array();
$handle = fopen("test.txt", "r");
if ($handle) {
    while (($line = fgets($handle)) !== false) {
        // process the line read.
        $line_ex = explode("|",$line);
        array_push($file_content,$line_ex);
    }
} else {
    // error opening the file.

}

echo "<pre>";
    print_r($file_content);
    echo "<pre>";
?>

then You will get below output

Array
(
[0] => Array
    (
        [0] => 99895
        [1] => 35378
        [2] => 0.01

    )

[1] => Array
    (
        [0] => 99895
        [1] => 813
        [2] => -0.97

    )

[2] => Array
    (
        [0] => 99895
        [1] => 771
        [2] => 0.29

    )

[3] => Array
    (
        [0] => 442
        [1] => 833
        [2] => -1.06

    )

[4] => Array
    (
        [0] => 442
        [1] => 485
        [2] => -0.61

    )

[5] => Array
    (
        [0] => 442
        [1] => 367
        [2] => -0.14

    )

[6] => Array
    (
        [0] => 442
        [1] => 478
        [2] => 0.77

    )

[7] => Array
    (
        [0] => 442
        [1] => 947
        [2] => -0.07

    )

[8] => Array
    (
        [0] => 7977
        [1] => 987
        [2] => 0.76

    )

[9] => Array
    (
        [0] => 7977
        [1] => 819
        [2] => 0.37

    )

[10] => Array
    (
        [0] => 7977
        [1] => 819
        [2] => 0.36

    )

[11] => Array
    (
        [0] => 7977
        [1] => 653
        [2] => 1.16

    )

[12] => Array
    (
        [0] => 7977
        [1] => 1653
        [2] => 1.15
    )

)

For determining average value from third column of corresponding first column - I am researching on it. When I will be done I'll put it here.

Alexander Yancharuk · Accepted Answer · 2013-12-19 12:40:17Z

1

Try this:

$filename = 'results.txt';
$result = $counter = $values = array();

$file = fopen($filename, 'r') or die("Couldn't open $filename");
while ($line = fgets($file)) {
    $content = explode('|', $line);
    if (empty($content[0]) or empty($content[2]))
        continue;

    $values[$content[0]][] = (float) $content[2];
    ++$counter[$content[0]];
}

foreach ($values as $key => $value) {
    $result[$key] = array_sum($value) / $counter[$key];
}
fclose($file);

edited Dec 19, 2013 at 12:40

answered Dec 19, 2013 at 12:10

Alexander Yancharuk

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