[R] outlier identify in qqplot

R. Michael Weylandt michael.weylandt at gmail.com
Thu Nov 17 07:00:01 CET 2011


Try this

qqInteractive <- function(..., IDENTIFY = TRUE){
     qqplot(...) -> X
     if(IDENTIFY) return(identify(X))
     invisisble(X)
}

The trick is that identify wants coordinates of the point in the
scatter plot which are not the inputs to qqplot() but rather a
transformation thereof.

Michael

On Wed, Nov 16, 2011 at 9:52 AM, agent dunham <crosspide at hotmail.com> wrote:
> Dear Community,
>
> I want to identify outliers in my data. I don't know how to use identify
> command in the plots obtained.
>
> I've gone through help files and use mahalanobis example for my purpose:
>
>
> NormalMultivarianteComparefunc <- function(x) {
>
>        Sx <- cov(x)
>        D2 <- mahalanobis(x, colMeans(x), Sx)
>        plot(density(D2, bw=.5), main="Squared Mahalanobis distances, n=nrow(x),
> p=ncol(x)")
>        rug(D2)
>        qqplot(qchisq(ppoints(nrow(x)), df=ncol(x)), D2,
>                main = expression("Q-Q plot of Mahalanobis" * ~D^2 *
>                         " vs. quantiles of" * ~ chi[ncol(x)]^2))
>
>        abline(0, 1, col = 'gray')
> }
>
> Then I run:
>
> NormalMultivarianteComparefunc(y); y dataframe with the data. Now, let's say
> y =replicate(5, rnorm(100))
>
> ##what should I write now to identify data from the plot??
> ##/identify(y)
> warning: no point within 0.25 inches
> /  ?????
>
> I know I can use aq.plot, but I would be very grateful if you could help me
> with identify.
>
> /By the way, in the function, how can the title write the value of the
> variables in spite of "ncol(x)" or "nrow(x)"/
>
> Thanks in advance, user at host.com
>
>
> --
> View this message in context: http://r.789695.n4.nabble.com/outlier-identify-in-qqplot-tp4076587p4076587.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org 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.
>



More information about the R-help mailing list