Dendrogram in R. How to make new tables by each cluster

Question

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library(mlbench)
library(stats)


College <- read.csv("colleges.XL.csv", header=T) ## this data has 23 columns
na.college<- na.omit(College)

row.names(na.college) <- NULL

na.college[, c(4:23)] <- scale(as.matrix(na.college[,c(-1,-2,-3)]))
###before making dendrogram, standardization is needed.

plot(hc<-hclust(dist(na.college[,c(-1,-2,-3)]),method="complete"),hang=-1)
##now the dendrogram is drawn.

groups <- cutree(hc, k=10) # cut tree into 5 clusters
# draw dendogram with red borders around the 5 clusters 
rect.hclust(hc, k=10, border="red")
## identifying 10 clusters by red borders

I want to make some tables from this dendrogram. I have 10 clusters and each cluster has elements presented as observation number( I can fine the observation numbers bottom of the dendrogram). As I can print the dendrogram as pdf file, I can copy all the observation numbers by drag and click.

Now the problem is, how can I make data tables by observation numbers? I want to make table whose columns are same with the original data of dendrogram, "na.college".

I want to make a data table of second cluster, but I do not know how to.

If you have any answers, please let me know.

Answer 1

Try this:

# your matrix dimensions have to match with the clustering results
# remove any columns from na.college, as you did for clustering
mat <- na.college[,-c(1:3)]

# select the data based on the clustering results
cluster_2 <- mat[which(groups==2),]

If you'd like to save all the clusters, it's best to do it as a list:

# each list entry will correspond to the cluster number
clust_list <- lapply(sort(unique(groups)), function(x) mat[which(groups==x),])

# to retrieve i.e cluster 2:
cluster_2 <- clust_list[[2]]