I need to generate a {0,1} matrix wifht nCr rows and n columns. The rows of the
matrix will consist of all possible combinations containing r ones.
My clumsy attempt for n = 6 and r = 3 is
X <- expand.grid(c(1,0),c(1,0),c(1,0),c(1,0),c(1,0),c(1,0))
Y <- X[rowSums(X)==3,]
I can genralize this in a function but the result is quite ugly. Any
suggestions?
Thank you in advance.
Martin
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