在stata中使用roccomp的问题

在stata11中使用roccomp的时候，帮助文档称各组数据可以使独立数据，也可以是相关数据，不知stata是如何自动辨别这两类数据的，因为毕竟比较的公式是不同的。有哪位先生指教一二？

roccomp expects the data to be in wide form when comparing areas
    estimated from the same sample (correlated data) and in long form for areas estimated from independent samples.

In Stata Manual [R] roc, you'll find  excellent examples (Example 3 and 4) of the use of roccomp on the same sample (correlated data) and on the independent samples.