Isotope with Fancybox filtering - fancybox

Question

I implemented Isotope.js into my WordPress site. I use it to display gallery with Easy Fancybox plugin to add zooming functionality for images. Problem is with Isotope filtering. I added rel attribute to my images but when I filter categories Fancybox still cycles through all images.
I need to add rel attribute dynamically based on category I'm filtering. I'm struggling with this problem for 3 days now. I've read bunch of post, tried view things but still can't make it work.
Most of posts give solution with data-fancybox-group attribute but I can't use it I must use rel attribute (it doesn't work for me anyway).
Here's my WP code:
<ul id="filters">
<li>All</li>
<?php
$terms = get_terms("polygraphy-categories");
$count = count($terms);
if ( $count > 0 ){
foreach ( $terms as $term ) {
echo "<li><a class='filterbutton' href='#' data-filter='.".$term->slug."'>" . $term->name . "</a></li>\n";
}
}
?>
</ul>
<?php $the_query = new WP_Query( 'post_type=polygraphy' ); ?>
<?php if ( $the_query->have_posts() ) : ?>
<div id="isotope-list">
<?php while ( $the_query->have_posts() ) : $the_query->the_post();
$termsArray = get_the_terms( $post->ID, "polygraphy-categories" );
$termsString = "";
foreach ( $termsArray as $term ) {
$termsString .= $term->slug.' ';
}
?>
<div class="<?php echo $termsString; ?> poli">
<?php
if ( has_post_thumbnail()) {
$full_image_url = wp_get_attachment_image_src( get_post_thumbnail_id(), 'full');
echo '<a class="fancybox" href="' . $full_image_url[0] . '" title="' . the_title_attribute('echo=0') . '" >';
the_post_thumbnail('thumbnail');
echo '</a>';
}
?>
</div>
<?php endwhile; ?>
</div>
<?php endif; ?>
And JS code:
jQuery(function ($) {
$(window).load(function(){
var $container = $('#isotope-list');
$container.isotope({
itemSelector : '.poli',
layoutMode : 'masonry'
});
var $optionSets = $('#filters'),
$optionLinks = $optionSets.find('a');
$optionLinks.click(function(){
var $this = $(this);
if ( $this.hasClass('selected') ) {
return false;
}
var $optionSet = $this.parents('#filters');
$optionSets.find('.selected').removeClass('selected');
$this.addClass('selected');
var selector = $(this).attr('data-filter');
$container.isotope({ filter: selector });
return false;
});
});
});
I was told that this code should work but it doesn't:
$('.filterbutton').on("click", function(){
var selector = $(this).attr('data-filter');
if(selector == "*"){
$(".fancybox").attr("rel", "gallery");
} else{
$(selector).find(".fancybox").attr("rel", selector);
}
return false;
});