给定约束，生成所有组合 [英] Generate all combinations given a constraint

问题描述

如何在4个块中生成2种处理（A，B）的6种组合的全部，从而在每个块中使用R来获得相等数量的A和B？

How can I generate all of the 6 combinations of 2 treatments (A,B) in blocks of 4, such that in each block there is an equal number of A's and B's, using R?

"AABB","ABAB","ABBA","BBAA","BABA","BAAB" 

PS组合的数量计算如下：

P.S. The number of combinations is calculated as follows:

如果

T = #treatments

n = #treatments in each block = k*T,

组合数等于 n！ / [k！* k！ （T次）]

谢谢

推荐答案

类似的事情应该起作用：

Something like this should work:

library(gtools)

t <- c('A','B')
k <- 2
n <- k * length(t)

t2 <- rep(t, k)
m <- permutations(n,n)
res <- unique(apply(m,MARGIN=1,function(x) paste(t2[x],collapse='')))

--------------------------------------------------------------------
res
[1] "ABAB" "ABBA" "AABB" "BAAB" "BABA" "BBAA"

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