op. sys. refuses to provide memory
    Stata's data-storage memory manager has already allocated 1664m bytes and it just attempted
    to allocate another 16m bytes.  The operating system said no.  Perhaps you are running
    another memory-consuming task and the command will work later when the task completes.
    Perhaps you are on a multiuser system that is especially busy and the command will work later
    when activity quiets down.  Perhaps a system administrator has put a limit on what you can
    allocate; see help memory.  Or perhaps that's all the memory your computer can allocate to
    Stata.
r(909);