Hi, Try: A <- as.data.frame(matrix(1:20,byrow=TRUE,ncol=4)) B <- as.data.frame(matrix(21:40,byrow=TRUE,ncol=4)) AB <- rbind(A,B) #if the ?row.names of both datasets are from 1:nrow(dataset) AB1 <- AB[order(as.numeric(c(row.names(A),row.names(B)))),] #or AB2 <- AB[c(matrix(seq(dim(AB)[1]),nrow=2,byrow=TRUE)),] #or AB3 <- AB[order(c(seq(dim(A)[1]),seq(dim(B)[1]))),] identical(AB1,AB2) #[1] TRUE identical(AB1,AB3) #[1] TRUE A.K. I want to merge two data frames with approximately same number of rows. But the merging needs to be done in a special way. Suppose the two data frames are A and B. and Ai, Bi represents the ith row of the respective data frames. Then I want a new dataframe with the following rows: A1 B1 A2 B2 . . . . Ai Bi . . . How do i efficiently do it in R ? Thank you.