[R] dendrogram - got it , just need to label :)

[Steven McKinney]

Here is one example of labeling nodes,
borrowing code from the help page for
the dendrapply() function.

local({
  edgeLab <<- function(n) {
      if(!is.leaf(n)) {
        a <- attributes(n)
        i <<- i+1
        attr(n, "edgetext") <-
            format(i)
      }
      n
  }
  i <- 0
 })
dL <- dendrapply(as.dendrogram(hclust(dist(iris[, 1:4]), method = "single")), edgeLab)
plot(dL)


This labels the edges above the nodes.

Martin Maechler and Robert Gentleman are developing the
dendrogram objects suite of functions.
As I have had to label nodes in S-PLUS, I'd like to put
in a request for a few more control parameters for
edge/internal node labeling control:

 - Allow the label without the polygon surrounding it.
   The polygon can obliterate too much of the dendrogram
   for larger sample sizes.  Perhaps an edgePar polygon
   plot logical p.plot taking values TRUE (default) and
   FALSE to omit the polygon.
 - Allow the label to appear near the node at the base
   of the edge.  Perhaps an edgePar text location parameter
   t.pos taking values in (0.0, 1.0) where 0.5 is in the
   middle of the edge (the default) and 1.0 is at the base 
   of the edge.

Since clusters are not always identified by 'cutting'
the dendrogram (e.g. in the iris single linkage
dendrogram plot we want to identify internal nodes that
are large runts or whose vertical edge lengths are
considerably longer than average) it is useful to be able
to identify nodes deeper in the tree.  This is aided
by having access to internal node labels/names and being
able to extract internal nodes by those labels/names.


Best

Steven McKinney

Statistician
Molecular Oncology and Breast Cancer Program
British Columbia Cancer Research Centre

email: smckinney at bccrc.ca

tel: 604-675-8000 x7561

BCCRC
Molecular Oncology
675 West 10th Ave, Floor 4
Vancouver B.C. 
V5Z 1L3
Canada




-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch on behalf of bunny , lautloscrew.com
Sent: Fri 3/9/2007 2:02 PM
To: R-help at stat.math.ethz.ch
Subject: [R] dendrogram - got it , just need to label :)
 
Hi all, Hi Gavin,

thx for your help i finally found out what i want to do and how to  
fix it.
just needed to get some more level my cut level was too small...

two question remain...

a) can i somehow scale the twigs after cutting ?
b) how can i label the nodes and how to label which one...

thx !!

-m.

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