Is there any way to programmatically distinguish between package environments and non-package environment objects? For example, the objects x and y below are both environments, with the same class and attributes.
x <- as.environment(cars)
y <- getNamespace("graphics")
However judging from the print method there is a difference:
> print(x)
<environment: 0x1d38118>
> print(y)
<environment: namespace:graphics>
Now suppose I have an arbitrary object, how can I determine which of the two it is (without looking at the output of print)? I would like to know this to determine how to store the object on disk. In case of the former I need to store the list representation of the environment (and perhaps its parents), but for the latter I would just store the name and version of the package.
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"
来源：https://stackoverflow.com/questions/19937824/how-to-distinguish-package-namespace-environment-from-other-environment-objects