Here are some sample conversions for basic vector types:

NULL is transformed to RNull:

Here is an internal form of a list of integers:

A list of reals:

A list of complex numbers:

A list of logical values (True or False):

A list of strings:

A list with missing elements:

However, lists of elements of different types will be interpreted as an R list. For example:

The previous example illustrates that the full internal RLink form is often rather inconvenient to work with.

Here is an internal form of an integer matrix:

You can notice three things here: first, matrix data is stored in a one-dimensional list. Second, the matrix is converted to a column-major order, since this corresponds to how it is stored in R. Finally, matrix dimensions are stored in the "dim" attribute.

Ragged (irregular) lists will be interpreted as R lists:

The same is true for lists containing elements of different types:

When you have to give your R object some extra attributes, you must wrap what you would normally construct in an RObject head and add attributes wrapped in an RAttributes head:

To perform the reverse operation and obtain a short form from the full internal form for a given expression representing some R object, you can use FromRForm:

The list, which is the value of the "myAtt" attribute for this object, was returned in a slightly different form. This is consistent with scalars being treated by R as one-element vectors, but can become a problem if you always rely on automatic type identification:

This problem and the recommended solution are discussed in more detail in the documentation page for RList.

Regardless of the way ToRForm interprets things, the cycle ToRForm to FromRForm should always return the same expression, except "dressing" scalars in extra lists.