How to define argument types for R functions?

Question

I am writing an R function, and I want to make sure that the argument of my R function is of a certain class (eg, \"matrix\").

What is the best way to do this?

S

Answer 1

Just for completeness: besides

is.matrix(foo) 

you can also test for

class(foo) == "matrix" 

which also works for non-standard that do not have is.foo() functions.