Ensures that an object is interpreted as a vector (array) when sent to the server language. The default strategy is to send length-1 vectors as scalars.
A vector object. Calling with a non-vector is an error.
the object, but with the S4 bit turned on. Relies on the convention that XR interfaces leave S4 objects as vectors, not scalars, even when they are of length 1
Chambers, John M. (2016) Extending R, Chapman & Hall/CRC. ( Chapter 12, discussing this package, is included in the package: ../doc/Chapter_XR.pdf.)