[Resolved] Variable Scope and Standard Deviation

[nlhowell]

This doesn't work:

function initConn($db,$table){
	global $conn,$rs;
	if(!$conn = new COM("adodb.connection")){
		print "<br>Could not create ADO connection.";
		//die;
	}
	else{
		print "<br>Connection created successfully.";
	}	
	if(!$strConn = "DRIVER=Microsoft Access Driver (*.mdb);DBQ=" . realpath($db) . ""){
		print "<br>Could not map database path. Check initConn calling.";
		//die;
	}
	else{
		print "<br>Database mapped successfully.";
	}
	$conn->open($strConn);

$rs = $conn->execute($table);
return $rs;

}

$strSQL= "SELECT * FROM pw WHERE password = '" . $_POST["password"] . "'";
print $strSQL;
$rs = initConn("db/pw.mdb",$strSQL);
$survey = $rs->fields["survey"]->value;
$conn->close();
$baseSQLa = "SELECT ";
$baseSQLb = " FROM results";



function calcDev($k){
//STANDARD DEVIATION
	global $baseSQLa, $baseSQLb;
	global $conn,$rs,$strSQL,$sum1,$sum2,$y,$x;
	$strSQL = $baseSQLa . "SUM(result" . $k . "^2) as sum1, SUM(result" . $k. ")^2 as sum2, COUNT(result" . $k . ") AS count" . $baseSQLb;
	$rs = initConn("db/".$survey.".mdb",$strSQL);
	print $strSQL;
	$sum1 = $rs->fields["sum1"]->value;
	$sum2 = $rs->fields["sum2"]->value;
	$y = $rs->fields["count"]->value;
	$conn->close();
	print "!" . $sum2 . "!";
	$x = ($y * $sum1)  - $sum2;
	return round((($x/($y*($y-1)))^0.5));
}
print calcDev(1);

While this does:

function initConn($db,$table){
	global $conn,$rs;
	if(!$conn = new COM("adodb.connection")){
		print "<br>Could not create ADO connection.";
		//die;
	}
	else{
		print "<br>Connection created successfully.";
	}	
	if(!$strConn = "DRIVER=Microsoft Access Driver (*.mdb);DBQ=" . realpath($db) . ""){
		print "<br>Could not map database path. Check initConn calling.";
		//die;
	}
	else{
		print "<br>Database mapped successfully.";
	}
	$conn->open($strConn);

$rs = $conn->execute($table);
return $rs;

}

$strSQL= "SELECT * FROM pw WHERE password = '" . $_POST["password"] . "'";
print $strSQL;
$rs = initConn("db/pw.mdb",$strSQL);
$survey = $rs->fields["survey"]->value;
$conn->close();
$baseSQLa = "SELECT ";
$baseSQLb = " FROM results";


$k = 1;
	$strSQL = $baseSQLa . "SUM(result" . $k . "^2) as sum1, SUM(result" . $k. ")^2 as sum2, COUNT(result" . $k . ") AS count" . $baseSQLb;
	$rs = initConn("db/".$survey.".mdb",$strSQL);
	print $strSQL;
	$sum1 = $rs->fields["sum1"]->value;
	$sum2 = $rs->fields["sum2"]->value;
	$y = $rs->fields["count"]->value;
	$conn->close();
	print "!" . $sum2 . "!";
	$x = ($y * $sum1)  - $sum2;
	print round((($x/($y*($y-1)))^0.5));
//print calcDev(1);

I think it has something to do with my variable scope, but I don't have much in the way of experience with that. Any ideas?

Thanks,
Nick

[barand]

It does seem strange that the version that leaves calcDev() as an undefined function and also does not define a value for $k should be the one that works. There should be an error that last line at least.

BTW hav you tried

"SELECT STDDEV(afield) AS dev FROM atablename"

[nlhowell]

Oops. The function I listed above does define a value for $k. I got that to work, was unsatisfied, and changed it back to play around with it more. Then I posted here, and did a quick re-do of what I was doing before.

The reason I am running StdDev off of a function is because I eventually have to combine multiple fields using UNION ALL, and then get the standard deviation of that.

Besides, I'm going to be using a median calculation, so I figure I might as well figure this out now, before I actually need to. Also, I am curious.

Nick

[nlhowell]

Never mind; all working. It was a really simple bug: I assigned a $_POST["survey"] var to a $survey, but forgot to mention it was global in my function.