[R] Odp: Permutation test, grouped data

[Petr PIKAL]

Hi


r-help-bounces at r-project.org napsal dne 02.11.2007 15:16:37:

> I am perfectly aware that this question is not an R question, at least 
> not yet, but I have not succeeded in finding what I want in other 
> ways, so ...
> 
> What I am looking for are two algorithms, preferabley in Pascal, but 
> other languages may do.  For (a) systematic (complete) permutations 
> for grouped data with unequal group sizes, and (b) random permutations 
> for the same kind of data.  I know of one source: E. S. Edgington 

I am not sure if it is what you want but

lll <- lapply(split(some vector, group vector), function(x) 
sample(1:length(x)))

gives you a list of systematic permutation of the first vector in each 
group and you can use it for subsetting your data. 

for (i in no.of.groups) split(data, group vector)[[i]] [lll[[i]],]

Random permutation (if I understand correctly) can be constructed by not 
exhaustive sampling so you can limit number of samples by size argument to 
sample function.

Regards
Petr

> (1980): Randomization Tests (program 4.1 and program 4.3), but those 
> are written in Fortran with a lot of GO TO's which probably would not 
> be very efficient even if I managed to manually these programs and do 
> a correct translation.  There must be some more modern ones around, 
> but where?
> 
> I need the algorithms for a program I have written for exploring 
> structural balance in sociometric group structures.
> 
> Tom
> 
> +----------------------------------------------------------------+
> | Tom Backer Johnsen, Psychometrics Unit,  Faculty of Psychology |
> | University of Bergen, Christies gt. 12, N-5015 Bergen,  NORWAY |
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