[R] label outliers in geom_boxplot (ggplot2)

[Mihalicza Péter]

Dear List and Hadley,

I would like to have a boxplot with ggplot2 and have the outlier values 
labelled with their "name" attribute. So I did
   
    > library(ggplot2)
    > dat=data.frame(num=rep(1,20), val=c(runif(18),3,3.5), 
name=letters[1:20])
    > p=ggplot(dat, aes(y=val, x=num))+geom_boxplot(outlier.size=4, 
outlier.colour="green")
    > p+geom_text(label=dat$name)

But this -of course- labels all the data points. So I searched high and 
low to find the way to only label the outliers, but I couldn't find any 
solution. Probably my keywords were inappropriate, but I looked at the 
ggplot website and  the book also. So I did this:
   
    > boxout=boxplot(dat$val)$out
    > outname=as.character(dat$name)
    > outname[(dat$val %in% boxout)==FALSE]="\n"
    > p+geom_text(label=outname)

This works, but seems like a hack to me. Is there an obvious solution 
that I am missing?


Another thing: it seems, that if there is only one outlier, ggplot 
doesn't show it, although it adjusts the axis to it, and also plots the 
label, when doing geom_text():
    >library(ggplot2)
    >dat=data.frame(num=rep(1,20), val=c(runif(19),3), name=letters[1:20])
    >ggplot(dat, aes(y=val, x=num))+geom_boxplot(outlier.size=4, 
outlier.colour="green")
    >p
    >p+geom_text(label=dat$name)

 > sessionInfo()
R version 2.6.2 (2008-02-08)
i386-pc-mingw32

locale:
LC_COLLATE=Hungarian_Hungary.1250;LC_CTYPE=Hungarian_Hungary.1250;LC_MONETARY=Hungarian_Hungary.1250;LC_NUMERIC=C;LC_TIME=Hungarian_Hungary.1250

attached base packages:
[1] splines   grid      stats     graphics  grDevices utils     datasets
[8] methods   base    

other attached packages:
[1] ggplot2_0.6        colorspace_0.95    RColorBrewer_1.0-2 
MASS_7.2-41      
[5] proto_0.3-8        reshape_0.8.0      Hmisc_3.4-3      

loaded via a namespace (and not attached):
[1] cluster_1.11.10 lattice_0.17-6  tools_2.6.2   

Thank you for your help!

Best wishes,
Peter


-- 
Peter Mihalicza
economist

National Institute for Strategic Health Research
6-8. Arany János utca, Budapest-1051, Hungary
www.eski.hu

Tel.: +36-1-354-5320
E-mail: mihalicza.peter at eski.hu



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