I’m newbie and I’m trying to create a plugin to add a menu to left menu in admin section.
i have create the page but it is working fine. but i find the left menu being displayed twice. how can I resolve the issue. Find below my code:

add_action('admin_menu','user_data');
    function user_data(){
      add_menu_page('User Data','User data','manage_options','user-page','user_data_options');
    }
    function user_data_options(){
        include('user-page.php');
    }