isNamespace
?
isNamespace(y)
# [1] TRUE
isNamespace(x)
# [1] FALSE
And, for future reference, apropos
is often helpful when you've got a question like this.
apropos("namespace")
# [1] "..getNamespace" ".BaseNamespaceEnv" ".getNamespace"
# [4] ".methodsNamespace" "asNamespace" "assignInMyNamespace"
# [7] "assignInNamespace" "attachNamespace" "fixInNamespace"
# [10] "getFromNamespace" "getNamespace" "getNamespaceExports"
# [13] "getNamespaceImports" "getNamespaceInfo" "getNamespaceName"
# [16] "getNamespaceUsers" "getNamespaceVersion" "isBaseNamespace"
# [19] "isNamespace" "loadedNamespaces" "loadingNamespaceInfo"
# [22] "loadNamespace" "namespaceExport" "namespaceImport"
# [25] "namespaceImportClasses" "namespaceImportFrom" "namespaceImportMethods"
# [28] "packageHasNamespace" "parseNamespaceFile" "requireNamespace"
# [31] "setNamespaceInfo" "unloadNamespace"