The inert function sync()
operates analogously to
ggplot2::waiver()
to indicate that an auxiliary aesthetic should be
synchronized to a standard aesthetic (when it is mapped from data).
is.sync()
reports whether an object is of this class.
sync()is.sync(x)
sync()
returns an empty list with the "sync"
class; is.sync()
returns a logical value of whether x
inherits this class.
An object to test