[R] combinations

[Dimitris Rizopoulos]

one possibility is:

treats <- t(combn(c("t01", "t02", "t03", "t04", "t05"), 2))

treats
# extract only t04
treats[apply(treats == "t04", 1, any), ]


I hope it helps.

Best,
Dimitris


On 8/18/2010 1:44 PM, Maas James Dr (MED) wrote:
> I would appreciate any suggestions on which function to use to write subsequent functions analysing combinations of treatments.
>
> This refers to experimental trials of medical treatments.  I want to write routines to analyse various comparisons (combinations)
>
> So .... if 5 treatments are available (t01, t02, t03, t04 and t05) I want to write a general routine that works out all possible combinations, without repeats.  The other complication is that I want to be able to designate any one of the treatments as the common comparator such that all other treatments are compared to it.
>
> For example, if I designate t04 as the common comparator then I want it to give me back some sort of vector or matrix with results
>
> t01, t04
> t02, t04
> t03, t04
> t05, t04
>
> In my research I've found functions such as combinations and permutations in gtools, and also choose().  I suspect these could be coerced to provide the correct output but I may be missing a specific, or more flexible package that will produce this.
>
> Any suggestions most welcome.
>
> Thanks
>
> Jim
>
> ===============================
> Dr. Jim Maas
> University of East Anglia
> Norwich, UK
>
> 	[[alternative HTML version deleted]]
>
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-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

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