[R] Match numeric vector against rows in a matrix?

Kevin Ummel kevinummel at gmail.com
Wed Jan 5 20:16:47 CET 2011

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)

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.


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