Hi all,
I use the following example to illustrate my question. As you can see,
in matrix C some rows are repeated and I would like to find the indices of
the rows corresponding to each of the distinct rows.
For example, for the row c(1,9), I have used the "which" function to
identify the row indices corresponding to c(1,9). Using this approach, in
order to cover all distinct rows, I need to use a for loop.
I am wondering whether there is an easier way where a for loop can be
avoided?
Thanks very much!
Hanna
> A <- matrix(c(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16),8,2)> B <-
> rbind(A,A,A)> C <- as.data.frame(B[sample(nrow(B)),])> C V1 V2
1 1 9
2 2 10
3 3 11
4 5 13
5 7 15
6 6 14
7 4 12
8 3 11
9 8 16
10 5 13
11 7 15
12 2 10
13 1 9
14 8 16
15 1 9
16 3 11
17 7 15
18 4 12
19 2 10
20 6 14
21 4 12
22 8 16
23 5 13
24 6 14> T <- unique(C)> T V1 V2
1 1 9
2 2 10
3 3 11
4 5 13
5 7 15
6 6 14
7 4 12
9 8 16> > i <- 1 > which(C[,1]==T[i,1]&
C[,2]==T[i,2])[1] 1 13 15
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