Foreach loop average of previous rows

Question

I have an foreach loop that takes some values from a MySQL database. The foreach it's very simple but with about 100 rows, like:

foreach($values as $value){}

what i'm trying to do but i don't know how it's to make inside the foreach the average of the previous 5 rows. So starting from the 5th row to do the average of the rows 1-5 then on the row 6 to do the average of rows 2-6 etc.

later edit, an simple example ex:

$values = array(1,2,3,4,5,6,7,8,9,10);
$i = 0;
foreach($values as $value){
if $i > 5{$average = (1+2+3+4+5)/5 }
// and here continue like if $i = 6 {$average = (2+3+4+5+6)/5}
// if $i = 7 {$average = (3+4+5+6+7)/5}
$i++;
}

Can you please elaborate more or show us an example of the expected outcome? — Ali
– Ali, Commented Oct 25, 2014 at 9:22
what do you want the result to look like.. an array with averages — N Kumar
– N Kumar, Commented Oct 25, 2014 at 9:26

Barmar · Accepted Answer · 2014-10-25 09:30:35Z

3

$total = 0;
foreach ($values as $i => $value) {
    $total += $value;
    if ($i >= 5) {
        $total -= $values[$i-5]; // Remove the oldest row
        $count = 5;
    } else {
        $count = $i+1;
    }
    $average = $total/$count;
}

answered Oct 25, 2014 at 9:30

Barmar

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Comments

Michael Smith · Accepted Answer · 2014-10-25 09:29:28Z

1

It's getting a bit late here (Australia) but I think something along the lines of.

$avg = array();
$averages = array();
$i = 0;
foreach($values as $value){
    $i++;
    echo $value;
    if($i <= 5){
        $avg[] = $value;
    }else{
        $calc = 0;
        foreach($avg as $a){
             $calc = $calc + $a;
        }
        $averages = $calc / 5;
    }
}

print_r($averages);

answered Oct 25, 2014 at 9:29

Michael Smith

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MH2K9 · Accepted Answer · 2014-10-25 09:40:24Z

1

You can use array_slice() for slice and array_sum() to calculate total then average. An example here

$values = array(1,2,3,4,5,6,7,8,9,10);
foreach($values as $k=>$v){
    if($k > 4){
       echo $ave = array_sum(array_slice($values, $k - 5, $k)) / 5 . '<br />';
    }
}

edited Oct 25, 2014 at 9:40

answered Oct 25, 2014 at 9:30

MH2K9

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1 Comment

Barmar Over a year ago

I think he wants running averages. This breaks the array up into separate groups of 5.

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