Poll Vote Percentages

CMellor · 11-28-2007, 07:29 PM

Hey all,

I think I got my poll to how I want it to work, though usually in my case, I get some form of an error, but I'll cross that bridge when I get to it. Any who... I basically want to calculate the percentage of the votes in my poll, so if their was one vote for 'yes' and one for 'no' then each would be 50%... you get the idea, I hope.

I'm no good with math in PHP, hell... math in general. Below is a structure of my poll tables, just to give you an idea of how things are laid out, so hope it helps.

poll

poll_id
question
creator_id
who_voted

poll_options

poll_options_id
from_poll_id
choice

poll_vote

vote_id
option_id
voter_id

Hope someone is kind enough to help me out :)

Wildhoney · 11-28-2007, 07:41 PM

You need to COUNT(*) all the choices that pertain to the poll_id you're after. Say you've got a total of 9 votes, take the 9 and store it. Then get all the options you have, COUNT them individually whilst using GROUP BY on the option they can select.

So if you have 5 yes, and 4 no, making a total of 9. You would do it like this (in pseudo form):

Code:

GET YES = 5
GET NO = 4
GET TOTAL = 9
GET PERCENT YES = 5 * 100 / 9
GET PERCENT NO = 4 * 100 / 9

Like you, I'm no good at maths. I have to nip out now but there's the theory. I hope someone helps you out properly, or at least I will when I return!

CMellor · 11-28-2007, 08:21 PM

Hey,

Thanks for the response, I'll definitely try that, though I'll admit I've never really had to use GROUP BY, so I'm not 100% on that one.

If you helped later on, that'd be great! :D

trmbne2000 · 11-30-2007, 04:36 PM

Hi, this is my first post... A way back I did a simple poll for a web site, here is a snippet from the code that displayed everything: (its an excrept from a class, but everything you need should be there)

PHP Code:


			
$pid = $this->pollID;

        $maxWidth = 120;

        $sql = "SELECT COUNT(ID) FROM poll_responses WHERE Poll_id = $pid";

        $rData = mssql_query($sql);

        $rRow = mssql_fetch_array($rData);

        $vCount = $rRow[0];

        $sql = "SELECT * FROM poll_answers WHERE Poll_id = $pid ORDER BY sOrd ASC";

        $rData = mssql_query($sql);

        $x = 1;

        $t = 0; //total counted

        $n = mssql_num_rows($rData); //number of questions

        if ($vCount != 0) {

        while($rRow = mssql_fetch_assoc($rData)) {

            $rid = $rRow["ID"];

            $txt = $rRow["Text"];

            $sql = "SELECT COUNT(ID) FROM poll_responses WHERE Poll_id = $pid AND Ans_id = $rid";

            $dData = mssql_query($sql);

            $dRow = mssql_fetch_array($dData);

            $newcount = $dRow[0];

            $avg = round(($newcount / $vCount),3);

            if ($x == $n) {

                $avg = 1 - $t;

            }

            $graphWidth = $maxWidth * $avg;

            $txtAvg = $avg * 100 . "%";

            print $txt . ": ($txtAvg)<br /><div id=\"graph$x\" style=\"height:7px; width:{$maxWidth}px; align:left; background-color:#" . $this->bbg . "; float: left; \"><img src=\"/includes/graph.php?color=" . $this->bc . "\" height=\"7\" width=\"$graphWidth\" align=\"middle\" alt=\"$txtAvg\" /></div><br />\r\n";

            $x++;

            $t = $t + $avg;

        } //while

        } else {

print("There are no votes yet");

}

I've never been big on group by for SQL either, so I took the less efficient route of just doing nested DB calls. Poll can be viewed in action at http://ww2.boatusangler.com/. If you need clarification on something, just ask, I'll do my best.

trmbne2000 · 11-30-2007, 04:37 PM

It also uses MSSQL, so its slightly different from mysql.

CMellor · 11-30-2007, 09:53 PM

Hey trmbne2000, thanks for the response, it's helped a bit.

Could I show you my function I've wrote? Perhaps someone may want to work off that? I'm not asking "Hey, do this for me" because that's the last thing I care for, as how else am I to learn, but, in this case, I've had an hectic two weeks in trying to find a job, and I always seem to have plans, so... if anyone could use my code and let me know what I could do to get the results I want, I'd appreciate it a lot!

PHP Code:


			
//--------------------
// Poll
//--------------------
function poll() {
    // Query
    $queryPoll = mysql_query(sprintf("
        SELECT poll_id, question, who_voted FROM poll
        WHERE creator_id = '%d'",
            getIdByUsername($_GET['uid'])
    )) or die(mysql_error());
    
    // Display content
    if($q = mysql_fetch_array($queryPoll)) {
        $output = '
        <form action="" method="post">
        <div class="sub-header">'.$q['question'].'</div>
          <div class="content-box">
        ';
        // Query for the options
        $queryOptions = mysql_query(sprintf("
            SELECT poll_options_id, choice FROM poll_options
            WHERE from_poll_id = '%d'",
                $q['poll_id']
        )) or die(mysql_error());
        
        $voted = unserialize($q['who_voted']);

        // Loop over options
        while($o = mysql_fetch_array($queryOptions)) {
            if(@in_array($_COOKIE['userID'], $voted)) {
                $queryVotes = mysql_query(sprintf("
                    SELECT COUNT(vote_id) AS total FROM poll_vote
                    WHERE option_id = '%d'",
                        $o['poll_options_id']
                )) or die(mysql_error());
                // Fetch
                $v = mysql_fetch_array($queryVotes);
                
                $output .= '
                <div class="poll-option">
                  '.$o['choice']. ' - ' .$v['total'].' - ' . round(100 * $v['total'] / 3, 2) .'
                </div>
                ';
            }
            else {
                $output .= '
                <div class="poll-option">
                  <input name="poll_choice" type="radio" value="'.$o['poll_options_id'].'" />&nbsp;'.$o['choice'].'
                </div>
                ';
            }
        }
        
        $output .= '
        </div>
        <div align="center">
        ';
        
        if(!@in_array($_COOKIE['userID'], $voted)) {
            $output .= '
            <input type="submit" value="Vote!" />
            ';
        }
        
        $output .= '
        </div>
        </form>
        ';
    }
    
    echo $output;
}

Thanks, really!

Off topic: I got the PM about the "award" not sure if I was given this personally by Wildhoney, or if you get it after the post count reaches the limit... either way, thanks!

Wildhoney · 11-30-2007, 09:57 PM

Remaining off-topic for the moment. All of them are personally handed out

trmbne2000 · 12-03-2007, 05:23 AM

Ok, the one thing I see is this line:

PHP Code:


			
'.$o['choice']. ' - ' .$v['total'].' - ' . round(100 * $v['total'] / 3, 2) .'

I may not be following your logic right, but it looks like you are dividing the number of votes for a particular option ($v['total']) by 3. I think what you want to do is divide the number of people who voted for a particular option by the total number of votes in that poll.