If I had a hierarchical dataframe like this:
level_1<-c("a","a","a","b","c","c")
level_2<-c("flower","flower","tree","mushroom","dog","cat")
level_3<-c("rose","sunflower","pine",NA,"spaniel",NA)
level_4<-c("pink",NA,NA,NA,NA,NA)
df<-data.frame(level_1,level_2,level_3,level_4)
How do I convert this to a list which orders according to the hierarchy, like this:
> list
[1] "a" "flower" "rose" "pink" "sunflower" "tree" "pine" "b" "mushroom" "c"
[11] "dog" "spaniel" "c" "cat"
So for in value in level 1, it list all level 2 values expanded across the other levels. Hopefully that makes sense?
Thanks in advance!
>Solution :
In the question "c" appears twice in the desired answer but "a" and "b" only appear once. We assume that this is an error and what is wanted is that each should only appear once.
uniq <- function(x) unique(na.omit(c(t(x))))
unname(unlist(lapply(split(df, df$level_1), uniq)))
## [1] "a" "flower" "rose" "pink" "sunflower" "tree"
## [7] "pine" "b" "mushroom" "c" "dog" "spaniel"
## [13] "cat"