On Jan 5, 2011, at 2:16 PM, Kevin Ummel wrote:
Two posts in one day is not a good day...and this question seems
like it should have an obvious answer:
I have a matrix where rows are unique combinations of 1's and 0's:
combs=as.matrix(expand.grid(c(0,1),c(0,1)))
combs
Var1 Var2
[1,] 0 0
[2,] 1 0
[3,] 0 1
[4,] 1 1
I want a single function that will give the row index containing an
exact match with vector x:
x=c(0,1)
> intersect( which(combs[,1]==x[1]), which(combs[,2]==x[2]) )
[1] 3
Or maybe even faster:
> which( combs[,1]==x[1] & combs[,2]==x[2])
[1] 3
The solution needs to be applied many times, so I need something
quick -- I was hoping a base function would do it, but I'm drawing a
blank.
--
David Winsemius, MD
West Hartford, CT
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