R help - Feb 2007 - Newbie: Acf function

Hi, I would like to use acf.plot on a correlogram that is computed 
externally. In other words, I would like to "fake out" the acf object.
Is this possible?-- any help would be appreciated.

TIA
Martin

Le Jeudi 8 F?vrier 2007 09:41, Martin Percossi a ?crit?:
> Hi, I would like to use acf.plot on a correlogram that is computed
> externally. In other words, I would like to "fake out" the acf
object.
> Is this possible?-- any help would be appreciated.
Well, essentially plot.acf() makes a plot with 'type = "h"'.
Playing around
with that so give you the desired output.

Now wait a little bit... There, I already wrote such a function:

tacf <- function(x, ...)
{
    plot(x, type = "h", ylab = "ACF", xlab =
"Lag",
         ylim = c(-1, 1), ...)
    abline(h = 0)
}

('x' contains the autocorrelations.)

HTH

-- 
  Vincent Goulet, Associate Professor
  ?cole d'actuariat
  Universit? Laval, Qu?bec 
  Vincent.Goulet at act.ulaval.ca   http://vgoulet.act.ulaval.ca

Martin Percossi wrote:
> Hi, I would like to use acf.plot on a correlogram that is computed 
> externally. In other words, I would like to "fake out" the acf
object.
> Is this possible?-- any help would be appreciated.
        (a) Note that it's ``plot.acf'' NOT acf.plot.

        (b) This is R --- ***ANYTHING*** is possible.

        (c) Create an object, say ``y'' of class ``acf'',
        having components with the right names.  You could
        build a dummy acf object by

                > dum <- acf(rnorm(100),plot=FALSE)

        and the examine ``dum'' to see what it should consist of.

        (d) Something like:

                y <- list(acf=array(ecc,dim=c(length(ecc),1,1)),
                          type="correlation",
                          n.used=n.ecc,lag=array(0:(length(ecc)-1),
                                                 dim=c(length(ecc),1,1)),
                          series="ecc",snames=NULL)
                class(y) <- "acf"
                plot(y)

        where ``ecc'' is a vector comprising your ``externally
        created correlogram'' and ``n.ecc'' is the length of the
series
        from which ecc was created.  Note that the first entry of ecc
        should be 1; it corresponds to lag 0.

                                        cheers,

                                                Rolf Turner
                                                rolf at math.unb.ca