Add Shortcode to RSS Excerpt in WordPress

/*
RE: http://wpthemetutorial.com/2012/02/14/removing-a-specific-shortcode-from-the_content/

Thank you for posting this. I have spent most of my afternoon trying to figure out how to efficiently see if a post had a shortcode in it. In my case, I needed to put an image in the RSS Excerpt... with variables from the shortcode. Here's my code for anyone is a simular situation:
*/

add_filter('the_excerpt_rss', 'rssexcerpt');
function rssexcerpt($rss_content) {
    global $post;
    $regex_pattern = get_shortcode_regex();
    preg_match('/'.$regex_pattern.'/s', $post->post_content, $regex_matches);
    if ($regex_matches[2] == 'YOUR_SHORTCODE') {
        $atts = str_replace(" ", "", $matches[3]); // this is some sort of invisible char that's not a space
        $atts = str_replace(" ", "&", $atts);
        $atts = str_replace('"', '', $atts);
        parse_str($atts, $atts);
        $rss_content = YOUR_SHORTCODE_FUNCTION($atts).$rss_content;
    }
    return $rss_content;
}