Dear R users,
I have noted a difference in the merge distances given by hclust using
centroid method.
For the following data:
x<-c(1009.9,1012.5,1011.1,1011.8,1009.3,1010.6)
and using Euclidean distance, hclust using centroid method gives the
following results:
> x.dist<-dist(x)
> x.aah<-hclust(x.dist,method="centroid")
> x.aah$merge
[,1] [,2]
[1,] -3 -6
[2,] -1 -5
[3,] -2 -4
[4,] 1 2
[5,] 3 4
> x.aah$height
[1] 0.50000 0.60000 0.70000 0.97500 1.36875
A calculation by hand results same merges, but at different distances for
latter stages:
heights:
0.5 => merging 3 and 6 => G1
0.6 => merging 1 and 5 => G2
0.7 => merging 2 and 4 => G3
*1.25 => merging G1 and G2 => G4
1.92 => merging G3 and G4*
It seems that hclust is not correctly computing the group centroids. Is it
correct?
Best regards,
Mateus
[[alternative HTML version deleted]]
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
