How To Exclude Specific Categories from RSS Feed

When you want to exclude specific categories from your WordPress RSS feed? Add this code to your theme’s functions file.

function exclude_category($query) {
    if ( $query->is_feed ) {
        $query->set('cat', '-5, -2, -3');
    }
return $query;
}
add_filter('pre_get_posts', 'exclude_category')