How to get labels from hclust result - r

Question

let's say i have a dataset like this
dt<-data.frame(id=1:4,X=sample(4),Y=sample(4))
and then i try to make a hierarchical clustering using the below code
dis<-dist(dt[,-1])
clusters <- hclust(dis)
plot(clusters)
and it works well
The point is when i ask for
clusters$labels
it gives me NULL, meanwhile i expect to see the label of indivisuals in order like
1, 4, 2, 3
it is important to have them with the order that they are added in plot

Answer 1

Use cluster$order rather than labels if you happened to not have assigned the labels.
Infact you can see all the contents by using function called summary
clusters <- hclust(dis)
plot(clusters)
summary(clusters)
clusters$order
You can compare with the plot i received at my end, it is offcourse little different than yours
My outcome:
> clusters$order
[1] 4 1 2 3
Content of summary command:
> summary(clusters)
Length Class Mode
merge 6 -none- numeric
height 3 -none- numeric
order 4 -none- numeric
labels 0 -none- NULL
method 1 -none- character
call 2 -none- call
dist.method 1 -none- character
You can observe that since there is null value against labels, hence you are not getting the labels. To receive the labels you need to assign them first using clusters$labels <- c("A","B","C","D") or you can assign with the rownames, once your labels are assigned you will no longer see the numbers you will able to see the names/labels.
In my case I have not assigned any name hence receiving the numbers instead.
You can put the labels in the plot function itself as well.
From the documentation ?hclust
labels
A character vector of labels for the leaves of the tree. By
default the row names or row numbers of the original data are used. If
labels = FALSE no labels at all are plotted.

Answer 2

You could use the following code:
# your data, I changed the id to characters to make it more clear
set.seed(1234) # for reproducibility
dt<-data.frame(id=c("A", "B", "C", "D"),X=sample(4),Y=sample(4))
dt
# your code, no labels
dis<-dist(dt[,-1])
clusters <- hclust(dis)
clusters$labels
# add labels, plot and check labels
clusters$labels <- dt$id
plot(clusters)
## labels in the order plotted
clusters$labels[clusters$order]
## [1] A D B C
## Levels: A B C D
Please let me know whether this is what you want.

Answer 3

Please make sure you use rownames(...) to ensure your data has labels
> rownames(dt) <- dt$id
> dt
id X Y
1 1 2 1
2 2 4 3
3 3 1 2
4 4 3 4
> dis<-dist(dt[,-1])
> clusters <- hclust(dis)
> str(clusters)
List of 7
$ merge : int [1:3, 1:2] -1 -2 1 -3 -4 2
$ height : num [1:3] 1.41 1.41 3.16
$ order : int [1:4] 1 3 2 4
$ labels : chr [1:4] "1" "2" "3" "4"
$ method : chr "complete"
$ call : language hclust(d = dis)
$ dist.method: chr "euclidean"
- attr(*, "class")= chr "hclust"
>