Hi List, Just wondering where the documentation exists for the statistics which makeup the bwplot. I'm guessing that if R is like similar products that the graph is constructed as The median is the filled circle. The box surrounding the filled circle depicts the 25th and 75th quartile. The range of values is given by the dotted lines (?whiskers?) outside of each box, and possible outliers are given by the open circles outside the box. Is this close? Thanks Kenneth E. Nussear Phone 775 784-1703 Ecology, Evolution and FAX 775 784-1369 Conservation Biology/314 knussear at biodiversity.unr.edu Reno, Nevada 89557-0013 http://www.brrc.unr.edu/~knussear/
bwplot() calls boxplot.stats() for the statistics, so look up ?boxplot.stats. Andy> -----Original Message----- > From: Ken Nussear [mailto:knussear at biodiversity.unr.edu] > Sent: Monday, February 24, 2003 11:44 AM > To: r-help at stat.math.ethz.ch > Subject: [R] bwplot stats question > > > > Hi List, > > Just wondering where the documentation exists for the > statistics which > makeup the bwplot. > > I'm guessing that if R is like similar products that the graph is > constructed as > > The median is the filled circle. The box surrounding the > filled circle > depicts the 25th and 75th quartile. The range of values is > given by the > dotted lines (?whiskers?) outside of each box, and possible outliers > are given by the open circles outside the box. > > Is this close? > > > Thanks > > > Kenneth E. Nussear Phone 775 784-1703 > Ecology, Evolution and FAX 775 784-1369 > Conservation Biology/314 knussear at biodiversity.unr.edu > Reno, Nevada 89557-0013 http://www.brrc.unr.edu/~knussear/ > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > http://www.stat.math.ethz.ch/mailman/listinfo/r-help >------------------------------------------------------------------------------
The documentation is 1) the code 2) ?boxplot 3) the standard references on EDA. I'd have to look up which exactly, but my guess would be to look at Velleman & Hoaglin (1981) ABC of EDA. Hoaglin, Mosteller, Tukey (1983) Understanding Robust and Exploratory Data Analysis. Some better references should be given on the help page. On Mon, 24 Feb 2003, Ken Nussear wrote:> Just wondering where the documentation exists for the statistics which > makeup the bwplot. > > I'm guessing that if R is like similar products that the graph is > constructed as > > The median is the filled circle. The box surrounding the filled circle > depicts the 25th and 75th quartile. The range of values is given by the > dotted lines (?whiskers?) outside of each box, and possible outliers > are given by the open circles outside the box. > > Is this close?Yes. They are I think hinges not quartiles (that's just a small difference in definition), and the whiskers extend to the most extreme data point less than 1.5*IQR outside the box. Points beyond the whiskers eare plotted separately: they would be unusual for a Normal sample. -- Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
On Mon, Feb 24, 2003 at 08:43:56AM -0800, Ken Nussear wrote: ...> Just wondering where the documentation exists for the statistics which > makeup the bwplot.It goes: bwplot calls panel.bwplot, which calls boxplot.stats help(boxplot.stats) gives you all you need to know, and more.> The median is the filled circle. The box surrounding the filled circle > depicts the 25th and 75th quartile. The range of values is given by the > dotted lines (?whiskers?) outside of each box, and possible outliers > are given by the open circles outside the box.For the whiskers, check out the "coef" argument to boxplot.stats. For now, because of the way it's nested, you can only use the default of 1.5 with bwplot. Sifting through the code, I don't see an easy, clean fix for this, but I'm not a very good R programmer. Cheers Jason -- Indigo Industrial Controls Ltd. 64-21-343-545 jasont at indigoindustrial.co.nz