tsp returns the tsp attribute (or NULL).
  It is included for compatibility with S version 2. tsp<-
  sets the tsp attribute. hasTsp ensures x has a
  tsp attribute, by adding one if needed.
tsp(x)
tsp(x) <- value
hasTsp(x)NULL.x only in the tsp attribute
  (unless NULL is assigned).hasTsp adds, if needed, an attribute with a start time and
  frequency of 1 and end time NROW(x).
tsp attribute gives the start time in time units,
  the end time and the frequency (the number of observations per unit of
  time, e.g.\ifelse{latex}{\out{~}}{ } 12 for a monthly series).Assignments are checked for consistency.
  Assigning NULL which removes the tsp attribute
  and any "ts" (or "mts") class of x.
ts, time, start.