I read the boxplot() help file and googled before making the post, and with my little knowledge on R I was not able to plot in the way I wanted. That’s why I made the post. Whether I can eventually solve the problem or not, I appreciate very much any help.
I’m a very beginner of R, and found the R help forum a couple of weeks ago. Since I thought I’m not among the major players of the forum and that the post per se rather than poster is of concern like in any other public online forum, I just registered with an arbitrarily chosen ID and kept using it. I’m not making use of R help for any commercial purposes whatsoever. I’m a master’s student working on my thesis. Thanks all for your help. Jimmy Gavin Simpson wrote: > > On Wed, 2009-08-19 at 13:49 -0700, Bert Gunter wrote: >> Rolf: >> >> Not sure what "reasonably thorough" means but: >> >> ? boxplot says: > > Exactly Bert, the info is there is you want to look and do so hard > enough. However, it is perhaps expecting quite a lot of a new useR to > put this together from ?boxplot or ?bxp, and ?boxplot.stats. > > Criticising correct, if cryptic or highlevel, responses to a list where > people give their time for free, *and* not provide a more complete > solution is unfair, Rolf. The OP is free to respond and ask for > additional help once they've given it a go if they are still having > trouble.. > > One solution, if you are prepared to bastardise the standard > interpretation of the boxplot, is to compute the relevant boxplot > statistics using boxplot.stats and alter argument 'coef' to some larger > multiple of the box height to represent "extreme" outliers, whatever > those might be. So here's the rope, try not to hang yourself 'Rnewbie'! > > set.seed(1234) > dat <- rt(100, df = 2) > bxp1 <- boxplot.stats(dat) > bxp2 <- boxplot.stats(dat, coef = 2) > > ##Then you'd need to plot the boxplot without outliers > > boxplot(dat, outpch = NA) > > ##Then plot the points 1.5-2 x box height > > want <- bxp1$out %in% bxp2$out > out <- bxp1$out > out[want] <- NA > > points(rep(1, length(out)), out, pch = 1, col = "blue") > > ##Then the further outliers > > outout <- bxp2$out > points(rep(1, length(outout)), outout, pch = 2, col = "red") > > How one decides what is an outlier or an extreme outlier is another > matter...? By chance the dummy data here shows one problem; there isn't > much difference between 'outliers' and 'extreme outliers' towards the > bottom of the resulting plot so why should we distinguish them? > > (By the way 'Rnewbie', this isn't something I recommend you do, but you > might know more about your real world use case than I.) > > HTH > > G > > Ps; is there a reason why you post anonymously, 'Rnewbie'? Do you not > want us to know who you are, but want our help? > >> >> ... >> pars a list of (potentially many) more graphical parameters, e.g., >> boxwex >> or outpch; these are passed to bxp (if plot is true); for details, see >> there. >> >> >> Well, that seems pretty clear to me, so I went to ?bxp to find in the >> pars >> listing: >> >> outlty, outlwd, outpch, outcex, outcol, outbg: >> outlier line type, line width, point character, point size expansion, >> color, >> and background color. The default outlty= "blank" suppresses the lines >> and >> outpch=NA suppresses points. >> >> >> It seems to me that this (and other omitted excerpts + examples) is at >> least >> a reasonable answer to the query (allowing the reader to at least infer >> that >> bxp does not distinguish degrees of outlyingness), so I don't understand >> your criticism. Feel free to respond privately if you prefer. >> >> -- Bert >> >> Bert Gunter >> Genentech Nonclinical Biostatisics >> >> -----Original Message----- >> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] >> On >> Behalf Of Rolf Turner >> Sent: Wednesday, August 19, 2009 1:27 PM >> To: ottorino-luca.pant...@unifi.it >> Cc: Rnewbie; ERRE >> Subject: Re: [R] mild and extreme outliers in boxplot >> >> >> On 20/08/2009, at 3:13 AM, Ottorino-Luca Pantani wrote: >> >> > Rnewbie ha scritto: >> >> dear all, >> >> >> >> could somebody tell me how I can plot mild outliers as a circle(°) >> >> and >> >> extreme outliers as an asterisk(*) in a box-whisker plot? >> >> >> >> Thanks very much in advance >> >> >> > ?boxplot >> > >> > or >> > >> > help(bxp) >> >> This is the sort of response that gives R-help a bad name. >> >> I had a reasonably thorough look at these help files and saw >> ***nothing*** >> that would answer the OP's question. The information may be there >> --- I'm >> not sure about this --- but it is far from obvious. Explicit reference >> to the appropriate lines of the help file(s) would be useful. >> >> cheers, >> >> Rolf Turner >> ###################################################################### >> Attention: >> This e-mail message is privileged and confidential. If you are not the >> intended recipient please delete the message and notify the sender. >> Any views or opinions presented are solely those of the author. >> >> This e-mail has been scanned and cleared by MailMarshal >> www.marshalsoftware.com >> ###################################################################### >> >> ______________________________________________ >> R-help@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. >> >> ______________________________________________ >> R-help@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. > -- > %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% > Dr. Gavin Simpson [t] +44 (0)20 7679 0522 > ECRC, UCL Geography, [f] +44 (0)20 7679 0565 > Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk > Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/ > UK. WC1E 6BT. [w] http://www.freshwaters.org.uk > %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% > > ______________________________________________ > R-help@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. > > -- View this message in context: http://www.nabble.com/mild-and-extreme-outliers-in-boxplot-tp25040545p25053573.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@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.
