\Header{WWWusage}{Internet Usage per Minute}
\keyword{datasets}{WWWusage}
\begin{Description}\relax
A time series of the numbers of users connected to the Internet
through a server every minute.
\end{Description}
\begin{Usage}
\begin{verbatim}data(WWWusage)\end{verbatim}
\end{Usage}
\begin{Format}\relax
A time series of length 100.
\end{Format}
\begin{Source}\relax
Durbin, J. and Koopman, S. J. (2001) \emph{Time Series Analysis by
State Space Methods.}  Oxford University Press.
\url{http://www.ssfpack.com/dkbook/}
\end{Source}
\begin{References}\relax
Makridakis, S., Wheelwright, S. C. and Hyndman, R. J. (1998)
\emph{Forecasting: Methods and Applications.} Wiley.
\end{References}
\begin{Examples}
\begin{ExampleCode}
data(WWWusage)
work <- diff(WWWusage)
par(mfrow = c(2,1)); plot(WWWusage); plot(work)
## Not run: 
aics <- matrix(, 6, 6, dimnames=list(p=0:5, q=0:5))
for(q in 1:5) aics[1, 1+q] <- arima(WWWusage, c(0,1,q),
    optim.control = list(maxit = 500))$aic
for(p in 1:5)
   for(q in 0:5) aics[1+p, 1+q] <- arima(WWWusage, c(p,1,q),
       optim.control = list(maxit = 500))$aic
round(aics - min(aics, na.rm=TRUE), 2)
## End(Not run)\end{ExampleCode}
\end{Examples}

