How do i change default wordpress function during my functions.php file?

To have an example in wordpress-includes/publish-template.php

function wp_dropdown_pages($args = '') {
$defaults = array(
 'depth' => 0, 'child_of' => 0,
 'selected' => 0, 'echo' => 1,
 'name' => 'page_id', 'id' => '',
 'show_option_none' => '', 'show_option_no_change' => '',
 'option_none_value' => ''
);
.... }

How do i change default option depth to five to have an example? I understand I must add_filter to wordpress_dropdown_pages. I'd appreciate any more assistance.