duangewu5234
duangewu5234
2013-11-15 14:42
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获取数组中每第n个值的平均值

I have the following array with they keys being unix timestamps, how can I get the average vlaue for example at an interval of every 30 seconds in a new array with the key being the 30 second interval?

array (size=61)
1375398000 => int 350
1375398015 => int 357
1375398030 => int 354
1375398045 => int 353
1375398060 => int 361
// and so on...

The desired output should be

1375398000 => int 353
1375398030 => int 354

I have tried some logic with using key($array) to get the first value but I cant figure out if this is working correctly inside a foreach loop.

My logic so far

     while($a <= $end){

    $chartData[$a] = $array[$a] //do the average here - current($array) / count($array);

}

I dont know how to get the next set of the keys and values to be used

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1条回答 默认 最新

  • dongzang5815
    dongzang5815 2013-11-15 15:40
    已采纳

    I'd do this, I'm sure this is not the most elegant, but it gets the job done.

    // Make sure the array is in the correct order
    ksort($charData);
    
    // This will be our new array
    $tmp = array();
    
    $interval = 30;
    
    // Set the array's pointer to the first element
    reset($charData); 
    $last_timestamp = key($charData);
    
    $total = 0;
    $count = 0;
    
    foreach ($charData as $timestamp => $value) {
        $total += $value;
        $count++;
    
        // If the current timestamp is newer 
        // than 30secs (or any interval set) we record the value
        if($timestamp - $last_timestamp >= $interval) {
            // Calculate the avg
            $tmp[$last_timestamp] = $total / $count;
    
            // Reset our helper vars
            $last_timestamp = $timestamp;
            $total = 0;
            $count = 0;
        }
    }
    
    $charData = $tmp;
    
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