I think Martin told you the basic approach to the indexing: averank<-sort(sample(1:100,25,replace=TRUE)) averank[-1] - averank[-length(averank)] [1] 1 1 6 3 4 14 1 1 8 1 2 6 5 4 10 0 3 2 1 11 1 1 2 0 averank [1] 4 5 6 12 15 19 33 34 35 43 44 46 52 57 61 71 71 74 76 77 88 89 90 92 92
----- Original Message ----- From: "IAIN GALLAGHER" <[EMAIL PROTECTED]> To: "Martin Henry H. Stevens" <[EMAIL PROTECTED]> Cc: <r-help@stat.math.ethz.ch> Sent: Monday, October 17, 2005 2:29 PM Subject: Re: [R] Dunn's post hoc test > Thanks for your reply Hank. It's not really what I'm > after (though it's good to know). > > For the test ( as described in Statistics for the > Biosciences by W. Gardiner. Prentice Hall, 1997) I > have to rank my groups, calculate the average rank, > then subtratc each average rank from every other. Any > value greater than the test statistic is significant. > > eg average rank difference table: > > 2 5 8 9 > ---|------------------ > 2 - 3 6 7 > | > 5 - - 3 4 > | > 8 - - - 1 > | > 9 - - - - > | > > I can't get my head around writing an algorithm for > this if I have a vector of average ranks eg averank<- > c(2,5,8,9). > > I know I can address the vector by index and that this > is probably the correct route but I can't get the > indexing algorithm right! > > I'm sure someone will point out somethng simple and > I'll kick myself but the help would be appreciated. > > Thanks again. > > Iain Gallagher > > --- "Martin Henry H. Stevens" <[EMAIL PROTECTED]> > wrote: > > > I don't know Dunn's rank test, but the following > > substracts each of > > the sums of averanks from the next rank. > > > > cumsum(averank)[-length(averank)] - averank[-1] > > > > Hank > > > > On Oct 17, 2005, at 4:30 AM, Iain Gallagher wrote: > > > > > Hi Everyone. > > > > > > I am rather new to R and I've been trying to > > implement a function to > > > carry out the above test. For a couple of days now > > I've been stuck on > > > how to generate average rank differences. > > > > > > Say I have a vector of average ranks: > > > > > > averank<- c(2,5,9,12) > > > > > > I would like to subtract averank[1] from > > averank[2], averank[1] and > > > averank[2] from averank[3] and averank[1], > > averank[2] and averank[3] > > > from averank[4] etc (I know the syntax is wrong > > here... it's just for > > > illustration) but I can't work out how to do it. > > > > > > Ideally I would like to generate an array showing > > the differences > > > between the average ranks so I could tell at a > > glance which ones were > > > greater than my critical value > > > > > > I've been looking at loops etc but it's a little > > beyond me at the > > > moment. Thanks for any suggestions. > > > > > > Iain Gallagher > > > IIIR > > > Edinburgh University > > > > > > ______________________________________________ > > > 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 > > > > > > > Dr. Martin Henry H. Stevens, Assistant Professor > > 338 Pearson Hall > > Botany Department > > Miami University > > Oxford, OH 45056 > > > > Office: (513) 529-4206 > > Lab: (513) 529-4262 > > FAX: (513) 529-4243 > > http://www.cas.muohio.edu/~stevenmh/ > > http://www.muohio.edu/ecology/ > > http://www.muohio.edu/botany/ > > "E Pluribus Unum" > > > > > > ______________________________________________ > 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 > ______________________________________________ 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