Tracked(mutable = TRUE, fixed = FALSE, labeled = TRUE,
hasAxis = FALSE, bgColor = "white", height = unit(1, "null"))TRUE. To control whether a track is
updatable by applying + on it.FALSE. To control whether the scale
response to a xlim change or not.TRUE. To control whether to label it
all not.FALSE. To control whether to show axis
for that track or not.Tracked object.