Please see Michael Frigge and David C. Hoaglin and Boris Iglewicz. "Some Implementations of the Boxplot". The American Statistician. Vol. 43 (1), February 1989. 50–54.
They investigate and compared several alternate definitions of the hinges (quartiles) and conclude that Tukey's definition is best on several criteria. ______________________________________________ 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.