From: Robert Baer <rbaer_at_atsu.edu>

Date: Tue 18 Oct 2005 - 08:26:32 EST

*> averank
*

[1] 15 29 30 31 31 38 52 66 82 94

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 Received on Tue Oct 18 08:33:09 2005

Date: Tue 18 Oct 2005 - 08:26:32 EST

I think I misunderstood your follow-up question. Try this:

*> averank<-sort(sample(1:100,10,replace=TRUE))
**> x=matrix(nrow=length(averank),ncol=length(averank))
**> for (i in 1:length(averank)){
*

+ for (j in 1:length(averank)){ + x[i,j] <- averank[i] - averank[j] + }}

> x

[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [1,] 0 -14 -15 -16 -16 -23 -37 -51 -67 -79 [2,] 14 0 -1 -2 -2 -9 -23 -37 -53 -65 [3,] 15 1 0 -1 -1 -8 -22 -36 -52 -64 [4,] 16 2 1 0 0 -7 -21 -35 -51 -63 [5,] 16 2 1 0 0 -7 -21 -35 -51 -63 [6,] 23 9 8 7 7 0 -14 -28 -44 -56 [7,] 37 23 22 21 21 14 0 -14 -30 -42 [8,] 51 37 36 35 35 28 14 0 -16 -28 [9,] 67 53 52 51 51 44 30 16 0 -12 [10,] 79 65 64 63 63 56 42 28 12 0

[1] 15 29 30 31 31 38 52 66 82 94

- Original Message ----- From: "IAIN GALLAGHER" <iaingallagher@btopenworld.com> To: "Martin Henry H. Stevens" <HStevens@MUOhio.edu> 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" <HStevens@MUOhio.edu>
**> 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

*>
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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 Received on Tue Oct 18 08:33:09 2005

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