

   SSaammpplliinngg TTiimmeess ooff TTiimmee--SSeerriieess

        time(x, offset=0)
        start(x)
        end(x)
        frequency(x)
        tsp(x)

   AArrgguummeennttss::

          x: a time-series.

   DDeessccrriippttiioonn::

        `time' creates the vector of times at which a time
        series was sampled.  `offset' can be used to indicate
        when sampling took place in the time unit.  `0' indi-
        cates the start of the unit, `0.5' the middle and `1'
        the end of the interval.

        `start' and `end' extract the times the first and last
        observations were taken and `frequency' returns the
        number of samples per unit time.

        `tsp(x)' returns the vector `c(start(x),end(x),fre-
        quency(x))'.  It is included for compatibility with the
        S language.

   SSeeee AAllssoo::

        `ts' and `system.time' for CPU usage.

   EExxaammpplleess::

        data(presidents)
        # a simple series plot
        plot(c(time(presidents)), c(presidents), type="l")

