Irregular Time Series Object
DESCRIPTION:
Constructs a univariate or multivariate time series with arbitrary sampling time intervals.
USAGE: 
its(x, times, units = NULL, names = NULL)
is.its(x)
REQUIRED ARGUMENTS:
x:
a vector, matrix, factor, or data frame containing the data values for the time series.
times:
either a numeric vector or a vector of class "dates" giving the times in ascending order at which successive observations are sampled.
OPTIONAL ARGUMENTS:
units:
character string giving the units in which the time domain is measured. This can also be an attribute of the vector times. (Default is NULL)
names:
(multivariate data only): a vector of character strings to be used as names for the component series of the multivariate series. The default is to use the dimnames for x if x is a matrix, or a data frame, or the strings "Series 1", "Series 2", ..., etc. if dimnames(x) = NULL. In the case of data frames, names overrides existing column names.
VALUE:
its returns an object of class "its" with data values given by x, and observation times given by times.

is.its returns TRUE if x is of class "its" and FALSE otherwise.

DETAILS:
The times vector is kept as the tspar attribute of the series. When the series is printed, only the first and last times of observation are printed.
SEE ALSO:
cts , dates , rts , units .
EXAMPLES: 
whitenoise <-  matrix(rnorm(50), ncol = 2)
obs.times <- scan("sampling.times") # reading in a file of times
x <- its(whitenoise, times = obs.times, names = c("error1","error2"))
is.its(x)


birthdays <- dates(c("01/02/78", "10/21/81", "06/23/86",
                       "01/19/90", "06/29/92"))
ages <- c(15, 11, 7, 3, 1)
its(ages, times = birthdays)