how to use the function from another package
Hi, I am trying to write a package(A) for myself and need to use a function from another package(B) which is in R already(need to install it before use). Could anyone tell me how to implement that? Also I hope that my package gives an ERROR message(something like "STOP, please install package B first") if the package B is not installed yet. It is my first time to write a package. Thanks very much for your help. Peter