[R] Dunn's post hoc test

[hadley wickham]

Or more simply:

averank<-sort(sample(1:100,10,replace=TRUE))
outer(averank, averank, "-")

Hadley

On 10/17/05, Robert Baer <rbaer at atsu.edu> wrote:
> 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
> > averank
>  [1] 15 29 30 31 31 38 52 66 82 94
>
>
>
> ----- Original Message -----
> From: "IAIN GALLAGHER" <iaingallagher at btopenworld.com>
> To: "Martin Henry H. Stevens" <HStevens at MUOhio.edu>
> Cc: <r-help at 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 at 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 at 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 at 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 at 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
>