PHP; Calculate Standard Deviation and Mean from Dreamweaver Recordset

Posted on 2013-05-26
Last Modified: 2013-05-26
Would like to calculate the mean and standard deviation from the 'id' field of a simple Dreamweaver Recordset which is:

mysql_select_db($database_conn_latestmysql, $conn_latestmysql);
$query_rst_price1 = "SELECT id FROM latest_ctry";
$rst_price1 = mysql_query($query_rst_price1, $conn_latestmysql) or  die(mysql_error());
$row_rst_price1 = mysql_fetch_assoc($rst_price1);
$totalRows_rst_price1 = mysql_num_rows($rst_price1);

Two difficulties:
1. correctly creating the array from the recordset
2. using the function sd($array).

Could anyone please help?
Question by:tweddlewalker
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LVL 110

Accepted Solution

Ray Paseur earned 500 total points
ID: 39197970
Do you have the function sd() code written yet?  If not, check this page.  It may or may not be part of your PHP installation.

This should help get things started.

mysql_select_db($database_conn_latestmysql, $conn_latestmysql);
$query_rst_price1 = "SELECT id FROM latest_ctry";
$rst_price1 = mysql_query($query_rst_price1) or  die(mysql_error());

$num = mysql_num_rows($rst_price1);

$ids = array();
while ($row = mysql_fetch_object($rst_price1))
    $ids[] = $row->id;

$sum = array_sum($ids);
$avg = $sum / $num;

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Author Closing Comment

ID: 39198077
Thank you for your help. It has unlocked the problem. Due to inexperience had omitted the line:
$ids[] = $row->id;

Now we can write:
  //calculate the variance
$the_variance = 0.0;
  for ($i = 0; $i < $num; $i++)
    //sum the array
    $the_variance = $the_variance + ($ids[$i] - $idsvg) * ($ids[$i] - $idsvg);
  $the_variance =$the_variance /$num-1;
  //now get the standard deviation

to complete the sequence and it works.
First rate
LVL 110

Expert Comment

by:Ray Paseur
ID: 39198110
Excellent!  Thanks for the points, ~Ray

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