indexing - Finding rows which match between 2 dataframes, and the index of them in R -

i have 2 dataframes. first (and know how this) want find rows (the whole row) match between 2 dataframes. can create column in tells me if entire row in b. however, part don't know how find indices in b be.

tl dr; need create new column in a, tells me false if whole row isn't in b, or instead give me index of row in b.

a = as.data.frame(matrix(data = 1:10,nrow=5)) b = as.data.frame(matrix(data = c(1:5,10,7,6,9,8), nrow=5))  set.seed(02138) b = b[sample(nrow(b)),] rownames(b) = 1:nrow(b) a_ = do.call("paste", a[,1:2]) b_ = do.call("paste", b[,1:2])  # gets me true/false of whether there complete row-wise match a$inb = a_ %in% b_  # gets me rows in b b[b_ %in% a_,]  # need combining # expected output  > a$inb = temp >   v1 v2   inb 1  1  6 false 2  2  7     3 3  3  8 false 4  4  9     5 5  5 10 false 

you can add this:

a$inb[a$inb] <- as.character(which(b_ %in% a_)) #  v1 v2   inb #1  1  6 false #2  2  7     3 #3  3  8 false #4  4  9     5 #5  5 10 false