

_T_i_m_e-_S_e_r_i_e_s _O_b_j_e_c_t_s

     ts(data = NA, start = 1, end = numeric(0), frequency = 1,
        deltat = 1, ts.eps = .Options$ts.eps)
     as.ts(x)
     is.ts(x)

     print(ts.obj, calendar, ...)
     plot(ts.obj, ...)

_A_r_g_u_m_e_n_t_s:

    data: a vector or matrix the observed time-series
          values.

   start: the time of the first observation.

     end: the time of the last observation.

frequency: the number of observations per unit of time.

  deltat: the fraction of the sampling period between suc-
          cessive observations; e.g., 1/12 for monthly data.
          Only one of `frequency' or `deltat' should be pro-
          vided.

  ts.eps: time series comparison tolerance.  Frequencies are
          considered equal if their absolute difference is
          less than `ts.eps'.

_D_e_s_c_r_i_p_t_i_o_n:

     The function `ts' is used to create time-series
     objects.  These are vector or matrices with class of
     `"ts"' (and additional attributes) which represent data
     which has been sampled at equispaced points in time.
     In the matrix case, each column of the matrix `data' is
     assumed to contain a single (univariate) time series.

     The value of argument `frequency' is used when the
     series is sampled an interal number of times in each
     unit time interval.  For example, one could use a value
     of `7' for `frequency' when the data are sampled daily,
     and the natural time period is a week, or `12' when the
     data are sampled monthly and the natural time period is
     a year.

     `start' and `end' can either be integers which
     correspond to natural time units, or vectors of two
     integers, which give a natural time unit and a (1-
     based) number of samples into the time unit.

     `as.ts' and `is.ts' respectively coerce a vector into a
     time-series and test whether an object is a time
     series.

     Time series have methods associated with the generic
     `print' and `plot' functions.  The argument `calendar'
     to the print method can be used to enable/disable the
     display of information about month names, quarter names
     or year when printing.

_S_e_e _A_l_s_o:

     `frequency', `start', `end', `time', `window'.

_E_x_a_m_p_l_e_s:

     ts(1:10, frequency = 4, start = c(1959, 2)) # 2nd Quarter of 1959
     print( ts(1:10, freq = 7, start = c(12, 2)), calendar = TRUE) # print.ts(.)
     ## Using July 1954 as start date:
     gnp <- ts(cumsum(1 + round(rnorm(100), 2)),
               start = c(1954, 7), frequency = 12)
     plot(gnp) # using `plot.ts' for time-series plot

     ts(1:10, frequency = 4, start = c(1959, 2)) # 2nd Quarter of 1959
     print( ts(1:10, freq = 7, start = c(12, 2)), calendar = TRUE) # print.ts(.)
     ## Using July 1954 as start date:
     gnp <- ts(cumsum(1 + round(rnorm(100), 2)),
               start = c(1954, 7), frequency = 12)
     plot(gnp) # using `plot.ts' for time-series plot

     ## A phase plot:
     data(nhtemp)
     plot(nhtemp, c(nhtemp[-1],NA), cex = .8, col="blue",
             main="Lag plot of New Haven temperatures")

     ## A phase plot:
     data(nhtemp)
     plot(nhtemp, c(nhtemp[-1],NA), cex = .8, col="blue",
             main="Lag plot of New Haven temperatures")

