The Interactive Matrix Language, which is the language of PROC IML, is not a "vector" language in R's sense. It is rather a "Matrix" language, since (1) the name says so; and (2) the fundamental (data) object in the language is not a vector (or 1 dim matrix), but a two-dimentional matrix. (see the "Defining a Matrix" section under "Understanding the Interactive Matrix Language" chapter of the SAS/IML User's Guide.