Hi, See the documentation for getWinner() here : <a href="https://github.com/julie

please give a sample code how to use advance method? <a class="user-mention notran

Do you mean this? Election->getWinner('advanced') <p dir="aut

I think you meant: <div class="highlight highlight-text-html-php notranslate posit

Hi <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="

Here is my code I am using: <a class="issue-link js-issue-link" data-error-text="Faile

getWinner & getName: various questions about condorcet HOT 10 CLOSED

julien-boudry commented on June 9, 2024

getWinner & getName: various questions

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Comments (10)

phplicengine commented on June 9, 2024

Now I believe there is bug with getName(), It happens when more than one candidate gets rank 1.

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julien-boudry commented on June 9, 2024

Hi,
See the documentation for getWinner() here : https://github.com/julien-boudry/Condorcet/blob/master/Documentation/Election%20Class/public%20Election--getWinner.md

If you use an advanced method instead of Natural, you can get an array with multiples winners.

Here, Schulze's method certainly produces a tie for first place, which may be normal, depending on the input votes. getWinner therefore returns an array.

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phplicengine commented on June 9, 2024

please give a sample code how to use advance method?
@julien-boudry

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phplicengine commented on June 9, 2024

Do you mean this?

Election->getWinner('advanced')

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julien-boudry commented on June 9, 2024

Election->getWinner() is always an advanced method. Default is 'Schulze Winning' method. Most of the advanced methods can produce a tie on rank, including top rank.

If you want the Natural Condorcet computation, the Marquis de Condorcet Winner. You must use Election->getCondorcetWinner() method. But be careful, the result can be NULL. The advanced methods almost always gives results, not the original Condorcet method.
https://github.com/julien-boudry/Condorcet/blob/master/Documentation/Election%20Class/public%20Election--getCondorcetWinner.md

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phplicengine commented on June 9, 2024

Here is my full source. If in form you choose the same number for more than one item, it gets error for getName() on getWinner(). What wrong I did as it is Schulze as you said.

use CondorcetPHP\Condorcet\Condorcet;
use CondorcetPHP\Condorcet\Election;
use CondorcetPHP\Condorcet\Candidate;
use CondorcetPHP\Condorcet\CondorcetUtil;
use CondorcetPHP\Condorcet\Vote;

if (isset($_POST) && $_POST != "") {
    
Condorcet::setDefaultMethod('Schulze');
$election = new Election ();

print("<pre>");
print_r($_POST['item']);

// To get Candidates by Category via Doctrine orm
$category = $em->getRepository('Entities\Category')->findOneBy(['id' => 1]);
$candidates = $category->getCandidates();

$total_items = 0;
foreach ($candidates as $candidate) {
         $candidate = $candidate->getCandidate();
         $election->addCandidate(new Candidate($candidate));
         ++$total_items;
}

$votes = array();
foreach ($_POST['item'] as $item => $ranking) {
    $vote_factor = 1 + $total_items - $ranking;
    if (isset($votes[$vote_factor])) {
       $votes[$vote_factor] = (array) $votes[$vote_factor];
       $votes[$vote_factor][] = $item;
    } else {
       $votes[$vote_factor] = $item;
    }
}    

$result = $election->addVote(new Vote($votes));  

print("<br />");
foreach ($election->getResult('Schulze') as $rank => $candidates) :
    echo 'Rank ' . $rank . ': ';
    echo implode(', ', $candidates);
    echo '<br />';
endforeach;

print_r($result->getSimpleRanking()); // To be saved in db.
echo 'Schulze winner is : ' . $election->getWinner('Schulze')->getName() . '<br />';
}

?>

<html>
    <body>
        <form method="post">
        Wingspan: <select name="item[Wingspan]" id="Wingspan">
                         <option value="1">1</option>
                         <option value="2">2</option>
                         <option value="3">3</option>
                         <option value="4">4</option>
                 </select><br />
        Scythe:  <select name="item[Scythe]" id="Scythe">
                         <option value="1">1</option>
                         <option value="2">2</option>
                         <option value="3">3</option>
                         <option value="4">4</option>
                 </select><br />
        Spirit Island: <select name="item[Spirit Island]" id="Spirit Island">
                         <option value="1">1</option>
                         <option value="2">2</option>
                         <option value="3">3</option>
                         <option value="4">4</option>
                  </select><br />
        Everdell: <select name="item[Everdell]" id="Everdell">
                         <option value="1">1</option>
                         <option value="2">2</option>
                         <option value="3">3</option>
                         <option value="4">4</option>
                  </select><br />
        <input type="submit" name="submit" value="submit">
        </form>
    </body>
</html>

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phplicengine commented on June 9, 2024

I think you meant:

foreach ($election->getWinner('Schulze') as $winner) {
    print($winner->getName()."<br />");
}

Is it correct? But it gives nothing if there is only one candidate. How do I know if there are only one or more than one winner(s) to fix this problem?

Please see my source, it seems it is working well, just for sure I want you to look at the source to see if everything is correct or any improvements you can suggest?

It seems

if (isset($_POST) && $_POST != "") {

is not working and for first run when there is nothing posted yet, I get these notices:

Notice:  Undefined index: item on line 19

Notice:  Undefined index: item on line 34

Warning:  Invalid argument supplied for foreach() on line 34.

Why I am getting these errors?
And is there any way to combine both foreach() as one and how to generate form items field from items fetched from db rather than hardcoding them?

I know these are not directly related to Condorcet, but I highly appreciate your help.

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julien-boudry commented on June 9, 2024

Hi @phplicengine,

Two ways.

$winners = $election->getWinner('Schulze');

if (is_array($winners) {
  foreach ($winners as $oneWinner) {
      echo($oneWinner->getName()."<br />");
  }
}
else {
    echo($winners->getName());
}

// On getResult, the ranks are always arrays.
  foreach ($election->getResult('Schulze')[1] as $oneWinner) {
      echo($oneWinner->getName()."<br />");
  }

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julien-boudry commented on June 9, 2024

About your problem with the $_POST in your code. I suppose that $_POST is always set (so your isset is useless) and is never an empty string. So, your condition is always true.

Look with empty() or count() or isset($_POST['item'])

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phplicengine commented on June 9, 2024

Here is my code I am using: #42 (comment)
I want to add a blank select option, that my users if they don't want to have some candidates in voting just use the blank select option and don't be forced to select a ranking number from the drop down menu. How to omit blank options completely from listing and voting? @julien-boudry

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getWinner & getName: various questions about condorcet HOT 10 CLOSED

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