R Question
Possible combinations of a matrix in R
I have a data frame as
df <- data.frame(x = c(1,2,3,4,5), y = c(11,12,13,14,15))
What I am trying to get is this
df
1 11
2 12
3 13
4 14
5 15
2 12
3 13
4 14
5 15
3 13
4 14
5 15
5 15
It basically is all the possible combinations of the data frame. I tried combn and expand.grid but they give me all possible combinations, not all possible combinations taken two at a time. I also tried looping it but the subsetting always goes for a toss.
Any ideas?
Answer
We can sequence by the pairs with an sapply iteration. Then binding the vectors with the index:
df <- data.frame(x = c(1,2,3,4,5), y = c(11,12,13,14,15))
s <- seq(length(df$x))
d2 <- unlist(sapply(s, seq, to=max(s)))
cbind.data.frame(x=df$x[d2], y=df$y[d2])
# x y
# 1 1 11
# 2 2 12
# 3 3 13
# 4 4 14
# 5 5 15
# 6 2 12
# 7 3 13
# 8 4 14
# 9 5 15
# 10 3 13
# 11 4 14
# 12 5 15
# 13 4 14
# 14 5 15
# 15 5 15
Source (Stackoverflow)