Question

I am attempting to build a Latency Area Chart using php and json to take datapoints I have in a MySQL database, and average them into 5 minute intervals. I am wondering if something like this is even possible.

Current Code:

mysql_select_db($mysql_db);
$query = ("select date, (delta_msec * .001) from www where agent_id in (45517,45655,42189,38583,45872,38678,38289,39074,38069,42096,37987,45182,38974,44956,38630,38297,38571,39181,39063,41992,38293,37978) and date >='" . date("Y-m-d H:i:s", strtotime("30 minutes ago")) . "' and date <= '" . date("Y-m-d H:i:s", strtotime("now"))  . "' order by date asc");
$result = mysql_query($query) or die($query. "<br/><br/>" .mysql_error());
while ($row = mysql_fetch_array($result)){
    $www[$q] = array("label" => $row[0], "value" => $row[1]);
    $q++;
}

When using

print_r ($www);

I am able to see the following (correct) Multi-dimentional array:

Array
(
[0] => Array
    (
        [label] => 2012-12-14 12:47:17
        [value] => 0.618
    )

[1] => Array
    (
        [label] => 2012-12-14 12:47:17
        [value] => 0.890
    )

[2] => Array
    (
        [label] => 2012-12-14 12:47:22
        [value] => 1.908
    )

[3] => Array
    (
        [label] => 2012-12-14 12:47:37
        [value] => 2.912
    )

[4] => Array
    (
        [label] => 2012-12-14 12:48:18
        [value] => 1.275
    )

[5] => Array
    (
        [label] => 2012-12-14 12:48:25
        [value] => 0.449
    )

[6] => Array
    (
        [label] => 2012-12-14 12:48:30
        [value] => 7.831
    )
)

The Array is MUCH larger than this, but I wanted to give a snippet of how it looks.

With this information I can convert this into JSON and FusionCharts will read all the values perfectly. However, it’s really just a reformatted “scatterplot” graph which doesn’t read well. I would like to be able to create another array from this Array so that I can basically make 5 minute buckets and average all of the values and do this for the past 4 hours.

I have only begun learning PHP, MySQL and fusioncharts (all at once) for about 2-3 weeks now and this is far beyond what I have learned. Would anyone be able to assist in creating an array like this? (or any other method?) Or would I only be able to do this by reformatting my SQL query to pull the data averaged already, and then make this call again for smaller versions of the graph?

Answer 1

You just need a function that will iterate over your array and group 5 items together and calculate the average. I threw this together:-

function get5MinAv(array $times)
{
    $result = array();
    $counter = 0;
    $temp['sum'] = 0;
    foreach($times as $time){
        if($counter == 0)$temp['start'] = $time['label'];
        $temp['sum'] += $time['value'];
        $counter ++;
        if($counter  == 5){
            $temp['av'] = $temp['sum']/5;
            $temp['end'] = $time['label'];
            $result[] = $temp;
            $temp['sum'] = 0;
            $counter = 0;
        }
    }
    return $result;
}

To test this I generated an array similar to yours:-

$interval = new DateInterval('PT1M');
$date = new DateTime();
$times = array();

for($i = 0; $i < 120; $i++){
    $times[$i]['label'] = $date->format('Y-m-d h:i:s');
    $times[$i]['value'] = 1;
    $date->add($interval);
}

and called it like this:-

var_dump(get5MinAv($times));

I have just put a value of 1 in to make checking easy, I have tested it with one or two other values and it all seems to work OK.

If you wished you could seed it with $times[$i]['value'] = rand(0, 1000)/100 to give a better range of values, but checking will be harder.

A sample of the output:-

array (size=24)
  0 => 
    array (size=4)
      'sum' => int 5
      'start' => string '2012-12-28 12:13:24' (length=19)
      'av' => int 1
      'end' => string '2012-12-28 12:17:24' (length=19)
  1 => 
    array (size=4)
      'sum' => int 5
      'start' => string '2012-12-28 12:18:24' (length=19)
      'av' => int 1
      'end' => string '2012-12-28 12:22:24' (length=19)
  2 => 
    array (size=4)
      'sum' => int 5
      'start' => string '2012-12-28 12:23:24' (length=19)
      'av' => int 1
      'end' => string '2012-12-28 12:27:24' (length=19)

Obviously, you can adjust this to suit your preferences, but this should get you started on the right track. A the moment this function will ignore any leftover times at the end that don’t form a group of 5. If you want to change that behaviour it will be a good exercise for you.