[R] expand.grip for permutations

[William Dunlap]

Instead of  
   rep(drugs, block.size)
use
   rep(list(drugs), block.size)
as the argument to expand.grid.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of trekvana
> Sent: Wednesday, October 31, 2012 1:18 PM
> To: r-help at r-project.org
> Subject: [R] expand.grip for permutations
> 
> if i were to have a block size of 4 people and i want to assign a treatment
> combination to the entire block, there would be 16 different treatment
> combinations (TTTT, TTTP, TTPP, PTTP, etc.)
> 
> i am trying to get all 16 permutations and i am able to use this code below.
> 
> drugs=c('P','T');
> comb=expand.grid(drugs,drugs,drugs,drugs)
> 
> for a block size of 3 the code would be comb=expand.grid(drugs,drugs,drugs)
> and for a block size of 2 it would be comb=expand.grid(drugs,drugs).
> 
> my question is whether there is a way to automatically create the comb
> variable. i tried using expand.grid(rep(drugs, block.size) but that didn't
> work.
> 
> any help on how i can proceed? thanks
> 
> 
> 
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