On Wed, Jan 05, 2011 at 07:16:47PM +0000, 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) > > 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.
If the matrix can have different number of columns, then also the following can be used combs <- as.matrix(expand.grid(c(0,1),c(0,1),c(0,1))) x <- c(0,1,1) which(rowSums(combs != rep(x, each=nrow(combs))) == 0) # [1] 7 Petr Savicky. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
