This code enables you to exclude any single page or pages from displaying in the sitemap.
The sitemap is generated when you create a new page and select the archive option from the drop down menu in the Page Attributes meta box located on the Edit Page screen as seen in the following image:
Why Hide Pages?
You might have a special download page for a eBook or after sign up page which you want to hide from your site visitors so they need to sign up before accessing protected downloads and content.
Here’s the code for members who can simply paste at the end of your functions file and swap out the page i.d with your own.