Running examples in ‘atom4R-Ex.R’ failed
The error most likely occurred in:

> base::assign(".ptime", proc.time(), pos = "CheckExEnv")
> ### Name: AtomFeed
> ### Title: Atom feed class
> ### Aliases: AtomFeed
> ### Keywords: atom feed
> 
> ### ** Examples
> 
>   #encoding
>   atom <- AtomFeed$new()
>   atom$setId("my-atom-feed")
>   atom$setTitle("My Atom feed title")
>   atom$setSubtitle("MyAtom feed subtitle")
>   author1 <- AtomAuthor$new(
+     name = "John Doe",
+     uri = "http://www.atomxml.com/johndoe",
+     email = "johndoe@atom4R.com"
+   )
>   atom$addAuthor(author1)
[1] TRUE
>   author2 <- AtomAuthor$new(
+     name = "John Doe's sister",
+     uri = "http://www.atomxml.com/johndoesister",
+     email = "johndoesister@atom4R.com"
+   )
>   atom$addAuthor(author2)
[1] TRUE
>   contrib1 <- AtomContributor$new(
+     name = "Contrib1",
+     uri = "http://www.atomxml.com/contrib1",
+     email = "contrib1@atom4R.com"
+   )
>   atom$addContributor(contrib1)
[1] TRUE
>   contrib2 <- AtomContributor$new(
+     name = "Contrib2",
+     uri = "http://www.atomxml.com/contrib2",
+     email = "contrib2@atom4R.com"
+   )
>   atom$addContributor(contrib2)
[1] TRUE
>   atom$setIcon("https://via.placeholder.com/300x150.png/03f/fff?text=atom4R")
>   atom$setSelfLink("http://example.com/atom.feed")
>   atom$setAlternateLink("http://example.com/my-atom-feed")
>   atom$addCategory("draft", "dataset")
[1] TRUE
>   atom$addCategory("world", "spatial")
[1] TRUE
>   atom$addCategory("fisheries", "domain")
[1] TRUE
>   #add entry
>   entry <- AtomEntry$new()
>   entry$setId("my-atom-entry")
>   entry$setTitle("My Atom feed entry")
>   entry$setSummary("My Atom feed entry very comprehensive abstract")
>   author1 <- AtomAuthor$new(
+     name = "John Doe",
+     uri = "http://www.atomxml.com/johndoe",
+     email = "johndoe@atom4R.com"
+   )
>   entry$addAuthor(author1)
[1] TRUE
>   author2 <- AtomAuthor$new(
+     name = "John Doe's sister",
+     uri = "http://www.atomxml.com/johndoesister",
+     email = "johndoesister@atom4R.com"
+   )
>   entry$addAuthor(author2)
[1] TRUE
>   contrib1 <- AtomContributor$new(
+     name = "Contrib1",
+     uri = "http://www.atomxml.com/contrib1",
+     email = "contrib1@atom4R.com"
+   )
>   entry$addContributor(contrib1)
[1] TRUE
>   contrib2 <- AtomContributor$new(
+     name = "Contrib2",
+     uri = "http://www.atomxml.com/contrib2",
+     email = "contrib2@atom4R.com"
+   )
>   entry$addContributor(contrib2)
[1] TRUE
>   entry$addCategory("draft", "dataset")
[1] TRUE
>   entry$addCategory("world", "spatial")
[1] TRUE
>   entry$addCategory("fisheries", "domain")
[1] TRUE
>   atom$addEntry(entry)
[1] TRUE
>   xml <- atom$encode()
Error in xmlSchemaValidate(xsd, xml) : 
  trying to get slot "ref" from an object of a basic class ("NULL") with no slots
Calls: <Anonymous> -> <Anonymous> -> xmlSchemaValidate
Execution halted