[BioC] dendrograms on heatmap.2 (gplots)

[Gavin Koh]

Dear all,

I have human Illumina gene expression data that I want to present in a
heatmap. I have already for the perfect heatmap using heatmap.2
(gplots) and RColorBrewer (R 2.13.0). I just want to put an dendrogram
on the columns, but the default behaviour of heatmap.2 is to reorder
the columns, which I do not want.

Reading the heatmap.2 help file, it looks like I would need hclust()
and dendrogram() to first generate the dendrogram (ideally
unsupervised k-nearest neighbours), which I can do easily, but again:
heatmap.2 will just reorder the columns according to the dendrogram.

Help, please? How do I get R to draw me a KNN dendrogram with two
clusters and add it to my heatmap without reordering it?

Thanks in advance,

Gavin.