I have data that looks like this:
> df1
group id
1 red A
2 red B
3 red C
4 blue D
5 blue E
6 blue F
I want a list of the groups containing vectors with the ids. I am
avoiding subset(), as it is
only recommended for interactive use. Here's what I have so far:
df1 <- data.frame(group=c("red", "red", "red", "blue", "blue",
"blue"), id=c("A", "B", "C", "D", "E", "F"))
groups <- levels(df1$group)
byid <- lapply(groups, "==", df1$group)
groupIDX <- lapply(byid, which)
> groupIDX
[[1]]
[1] 4 5 6
[[2]]
[1] 1 2 3
This gives me a list of the indices for each group. I want to subset
df1 based on this list.
If I want just one group I can do this:
> df1[groupIDX[[1]],]$id
[1] D E F
What sort of statement should I use if I want a result like:
[[1]]
[1] D E F
Levels: A B C D E F
[[2]]
[1] A B C
Levels: A B C D E F
So far, I've used a for loop. Can I express this with apply statements?
groupIDs <- list(1:length(groupIDX))
groupData<-
for (i in 1:length(groupIDX)) {
groupIDs[[i]] <- df1[groupIDX[[i]],]$id
}
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