Category breakdown

add_filter('relevanssi_hits_filter', 'rlv_search_result_cats');
function rlv_search_result_cats( $hits ) {
    global $rlv_search_result_cats;
    $rlv_search_result_cats = array();
    if ( ! empty( $hits ) ) {
        foreach ( $hits[0] as $hit ) {
            $cats = get_the_category( $hit->ID );
            if ( $cats ) {
                foreach ( $cats as $cat ) {
                   $rlv_search_result_cats[$cat->cat_name]++;
                }
            }
        }
    }
    return $hits;
}