I often need to retrieve number of samples or features of a given ExpressionSet. I use constructs like dim(es)[[2]], and just to make my code easier to read I wrapped it into functions, so that I can call it like nSamples(es). Hence two questions:
1) Maybe there's already a function for that?
2) if not, is it a good practice to use dim() for that purpose, or I should call something else?

nrow() and ncol() return features and samples directly, although these are not as semantically rich as nSamples()

> nrow(ExpressionSet())
Features
       0
> ncol(ExpressionSet())
Samples
      0