R devel - Jan 2011 - Possible bug in cut.dendrogram when there are only 2 leaves in the tree ?

Hello,

I noticed a behavior ot the cut() function that does not seem right. In a
dendrogram with only 2 leaves in one cluster, if you cut()
at a height above this cluster, you end up with 2 cut clusters, one for each
leaf, instead of one.

But it seems to work fine for dendrograms with more than 2 objects.

For instance:

library(stats)
m <- matrix(c(0,0.1,0.1,0),nrow=2, ncol=2)
dd <- as.dendrogram(hclust(as.dist(m)))
#plot(dd)
print(cut(dd, 0.2)) # 2 clusters in $lower

m2 <- matrix(c(0,0.1,0.5,0.1,0,0.5,0.5,0.5,0),nrow=3, ncol=3)
dd <- as.dendrogram(hclust(as.dist(m2)))
print(cut(dd, 0.2)) # here 2 clusters in $lower, as expected

So the question is: is it expected behavior that the whole tree is not
reported in the $lower if it is itself under the threshold ?

Thank you,

Karl FORNER

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