[R] Box plot with 5th and 95th percentiles instead of 1.5 * IQR: problems implementing an existing solution...

From: Paul Raftery <p.raftery_at_gmail.com>
Date: Sun, 17 Apr 2011 12:08:52 +0100


Hi all,

I'm just getting started with R and I would appreciate some help. I'm having trouble creating a boxplot with whiskers at the 95th and 5th percentiles instead of at 1.5 * IQR. I have read the relevant documentation, and checked existing mails on this topic. I found a small modification that should work : https://stat.ethz.ch/pipermail/r-help/2001-November/016817.html and tried to implement it.

Basically, it says to replace boxplot.stats with:

myboxplot.stats <- function (x, coef = NULL, do.conf = TRUE, do.out = TRUE)
{
  nna <- !is.na(x)
  n <- sum(nna)
  stats <- quantile(x, c(.05,.25,.5,.75,.95), na.rm = TRUE)   iqr <- diff(stats[c(2, 4)])
  out <- x < stats[1] | x > stats[5]
  conf <- if (do.conf)
    stats[3] + c(-1.58, 1.58) * diff(stats[c(2, 4)])/sqrt(n)   list(stats = stats, n = n, conf = conf, out = x[out & nna]) }

I entered the new function, and used fix(boxplot.default) to modify boxplot.default so that it references myboxplot.stats instead of the original boxplot.stats function.

If I now type boxplot.default, I can see that the code has been modified as expected. However, I get the exact same result as before when I create a boxplot - it shows the whiskers at 1.5 * IQR. You can test this out by creating a boxplot from the iris dataset supplied with R using boxplot(iris$Sepal.Length ~ iris$Species). You see that the boxplot is the same before and after the fix. Does anybody know why this occurs, and how I can get around this issue?

Thanks,

-- 
Regards,
Paul



=====================
Contact Details
=====================
Paul Raftery, BEng(Hons) (Mech), Fulbright Fellow, PhD http://www.paulraftery.com/ <http://www.paulraftery.com/> Postdoctoral Research Engineer Informatics Research Unit for Sustainable Engineering (IRUSE) http://www.iruse.ie/ Department of Civil Engineering, National University of Ireland, Galway, University Road, Galway, Ireland. Landline: +353 91 49 3086 Mobile: +353 85 124 7947 Skype: praftery [[alternative HTML version deleted]] ______________________________________________ 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.
Received on Sun 17 Apr 2011 - 21:09:34 GMT

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