

   CCaallccuullaattee aanndd pplloott aa ppeerriiooddooggrraamm

        pergram(y)
        plot.pergram(y, add=F, lty=1, xlab="Frequency", ylab="Periodogram",
             main="Periodogram", ylim=c(0,max(po[,2])))
        plot.cum.pergram(y, xlab="Frequency", ylab="Periodogram",
             main="Cumulative periodogram",
             ylim=c(0,max(cpo+1.358/(a+0.12+0.11/a))))

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

          y: A time series vector.

        add: If TRUE, adds a new periodogram to an existing
             plot.

     others: Graphics parameters

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

        `pergram' calculates the values of a periodogram,
        `plot.pergram' plots it, and `plot.cum.pergram' plots
        the corresponding cumulative periodogram.

   VVaalluuee::

        `pergram' prints and returns a two-column matrix of
        class, `pergram', containing the periodogram.

   AAuutthhoorr((ss))::

        J.K. Lindsey

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

        y <- rnorm(100)
        print(z <- pergram(y))
        plot(z)
        plot.cum(z)

