sorting article by class with checkboxes

I try to sort out the members of a team by the function they has in the company.

actually it sorts with an AND function: If member A has function 1 and member B has function 2 and I select the checkboxes for function 1 and for function 2 it will show me member A and member B

but now I need an OR function:

so if member A has function 1 and function 2 and member B has function 2 and I select checkbox for function 1 and for function 2 it should show me only member 1 because he has both functions

Here's my jQuery:

jQuery(document).ready(function($) {
$('div.tags').delegate('input:checkbox', 'change', function()
{
     var $lis = $('.results > article').hide();
     //For each one checked
     var numChecked = $('input:checked').each(function()
     {
          $lis.filter('.' + $(this).attr('rel')).show();
     }).length;

    if (!numChecked) $lis.show();
});
}); 

Here's my HTML:

<section class="squad results">
    <article class="function1 function2 function3 ">
        <p class="member-name"><b>Member A</b></p>
    </article>
    <article class="function1">
        <p class="member-name"><b>Member B</b></p>
    </article>
    <article class="function2 ">
        <p class="member-name"><b>Member C</b></p>
    </article>
</section>

How can I simple change this to sort by OR?

Thanks.