From: Matthias Braeunig <mb.atelier_at_web.de>

Date: Sat 19 Aug 2006 - 04:56:36 EST

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Date: Sat 19 Aug 2006 - 04:56:36 EST

Hi Stefano,

the manual tells us that we can access components of an acf object directly by acf.obj[.], but assignment ]<- does not work this way.

One way of doing what you want is to assign NA to x$acf[x$lag==0] like so:

x <- acf(runif(100))

x$acf[1] <- NA

plot(x)

But I suppose what you actually want is to have a reasonable ylim to be in effect when plotting your acf. I have struggled with this myself and found the following solution:

In plot.acf the formula for the white noise confidence interval is something along the lines of

acf.clim <- function(x=stop("your acf"), n=x$n.used, CL=.95) {

cl = qnorm((1+CL)/2)/sqrt(n) attr(cl,"CL") <- CL return( cl)

}

Using this function you can plot

x <- acf(runif(100),plot=F)

plot(x, ylim=2*acf.clim(x)*c(-1,1)) # adjust magnification as needed

As for your second question we first prevent plotting of x-axis and then add our custom axis:

x <- acf(runif(1000),100,plot=F)

plot(x, ylim=2*acf.clim(x)*c(-1,1),xaxt='n') # note option 'xaxt'!
axis(1,at=12*(0:8))

Hope that helps,

Matthias

NB: It would be a good idea to include the acf.clim(.) inside of the acf object... Now it is somewhat hidden inside of plot.acf

x$clim <- acf.clim(x)

str(x)

Stefano Sofia wrote:

> I need to modify the graph of the autocorrelation. I tried to do it through plot.acf but with no success.

*>
**> 1. I would like to get rid of the lag zero
**> 2. I would like to have numbers on the x-axis only at lags 12, 24, 36, 48, 60, ...
**>
**> Could anybody help me in this?
**>
**> Any help will be appreciated
**> Thank you for your attention
**> Stefano
**>
**>
**> [[alternative HTML version deleted]]
**>
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-- Journalist: "Mr. Gandhi, what do you think of Western civilization?" Gandhi: "I think it would be a good idea." ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ Matthias Braeunig, Dipl.Phys. ~ University Medical Center Freiburg ~ Institute of Environmental Medicine and Hospital Epidemiology ~ Department of Evaluation Research in Complementary Medicine ~ Hugstetter Str. 55, D - 79106 Freiburg, Germany ~ Phone: +49 (0)761 270-8306, Fax: -8343 ~ Web: http://kompmed.uniklinik-freiburg.de ~ Email: matthias.braeunig@uniklinik-freiburg.de ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.Received on Sat Aug 19 05:02:29 2006

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