Hi Ben, I like the odd looking notches, they reveal that the data comprising the box plot need more careful review.
Tukey et al (1) comment that "It should be noted that the convention has been adopted that, should the notch lie outside either hinge, an unnotched box, plotted with dashed lines, is displayed for that group indicating low confidence in it." While this convention appears to have been abandoned, the wierd-looking notches indicate a group with odd behaviour warranting more careful consideration. So I vote to retain odd-looking notches. Et al and Tukey (1) discuss their reasoning and empirical findings as to the formulation for the notch width. They used median +/- 1.7(1.25R/1.35sqrt(N)) which reduces to median +/- 1.574*(IQR)/sqrt(N) Perhaps similar reasoning can resolve the issue of notches for boxplots of log(y)? I'll see if I can work through the normal - lognormal transformation machinery and propose a reasonable notch strategy for the log(y) case. Maybe someone out there has already done so? (1) R. McGill, J. Tukey, W. Larsen (1978) "Variations of Box Plots" The American Statistician, Vol. 32, No. 1, pp 12-16 http://www.jstor.org/view/00031305/di020553/02p0045u/0 Cheers Steven McKinney Statistician Molecular Oncology and Breast Cancer Program British Columbia Cancer Research Centre email: [EMAIL PROTECTED] tel: 604-675-8000 x7561 BCCRC Molecular Oncology 675 West 10th Ave, Floor 4 Vancouver B.C. V5Z 1L3 Canada -----Original Message----- From: [EMAIL PROTECTED] on behalf of Ben Bolker Sent: Tue 10/17/2006 6:09 AM To: r-devel@stat.math.ethz.ch Subject: Re: [Rd] boxplot, notches, etc. Ben Bolker <bolker <at> zoo.ufl.edu> writes: > > Synopsis: boxplot notches look weird when notches > are greater than hinges ((1.58*IQR/sqrt(n)) > approx IQR). > When log="y" this causes an error. Below are several > reproducible examples, some discussion, and a patch against > calc.R. > > Please feel free to say "this is just cosmetic/isn't an issue, go > away" ... > > cheers > Ben Bolker > followup (one week later): does anyone have any opinions on this ... ??? (If someone will tell me this isn't worth pursuing, I will give up on it) Ben Bolker ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
