moving average

[nexx]

Im trying to calculate a moving average, however I cant get it to work.

$result = @mysql_query("SELECT  close, FROM am where sdate BETWEEN '2004-03-01' AND '2004-03-30'ORDER BY sdate");     

while($row = mysql_fetch_assoc($result))
{
    $count =+1;
    $total =+$row['close'];
    if(count==5){
    $res=$total/5;
    $array[] = $res;
    $count =0;
    }
}

this will only calculate everage for every 5 days. Im strugling to make it a moving average.

a 5-day simple moving average is calculated by adding the prices for the last 5 days and dividing the total by 5.

10+11+12+13+14 = 60/5

if the next closing price in the average is 15, then this new period would be added and the oldest day, which is 10, would be dropped. The new 5-day simple moving average would be calculated as follows:

11+12+13+14 +15 = 65/5

Im not sure how to drop 10 from the equation and start while loop from 11.

Could anyone advise

[bubblenut]

Not quite sure what you mean about droping the 10 but you can do averages in the sql

SELECT AVG(close) FROM am WHERE sdate BETWEEN '2004-03-01' AND '2004-03-30'ORDER BY sdate LIMIT 5;

HTH
Bubble

[nexx]

Thank you for your reply

SELECT AVG(close) FROM am WHERE sdate BETWEEN '2004-03-01' AND '2004-03-30'ORDER BY sdate LIMIT 5;

Not what Im trying to do.

Im trying to calculate avg for data in a period of 5 days so I have avg for 1-5 of March then 2-6 of March then 3-7 and so on.

[sidney]

this will do a rolling average.

first few days will be averaged by the number of days in days array

once days array reaches five elements it starts overwriting the oldest

untested

 
$count=0;
while($row = mysql_fetch_assoc($result)) 
{ 
	if($count==5)
		$count=0; 
    $days[$count]=$row['close']; 
    $total = array_sum($days);
	$res=$total/count($days); 
	$count++;    

} 

[nexx]

Hi Sid, thanx a lot for your help.

it works, though dont quite understand why you put $row['close'] into $days[$count] does it create an associative array with $count as keys for 'close' as values?

$days[$count]=$row['close'];  

Also I need moving avg for 1-5 of march then 2-6 then 3-7 and so on untill the end of the month(e.g between 1 of march to 30th). but it should be one result for every 5 days.

[sidney]

 $days[$count]=$row['close']; 

produces an array with keys 0-4 as count is set to 0 when it reaches 5

 {  

    if($count==5) 
        $count=0;  

    $days[$count]=$row['close'];  

    $total = array_sum($days); 
    $res[]=$total/count($days);  

    $count++;     

} 

for($i=4;$i<count($res);$i++)
         echo $res[$i]."<br>";