Question: I have two dendrograms which I wish to compare to each other in order to find out how "similar" they are. But I don't know of any method to do so (let alone a code to implement it, say, in R).

Any leads ?

**UPDATE** (2014-09-13):

Since asking this question, I have written an R package called [dendextend](http://cran.r-project.org/web/packages/dendextend/), for the visualization, manipulation and **comparison** of dendrogram. This package is on [CRAN](http://cran.r-project.org/web/packages/dendextend/) and comes with a [detailed vignette](http://cran.r-project.org/web/packages/dendextend/vignettes/introduction.html). It includes functions such as `cor_cophenetic`, `cor_bakers_gamma` and `Bk` / `Bk_plot`. As well as a `tanglegram` function for visually comparing two trees.

Answer: 
As you know, [Dendrograms](https://www.centerspace.net/drawing-dendrograms) arise from hierarchical clustering - so what you are really asking is how can I compare the results of two hierarchical clustering runs. There are no standard metrics I know of, but I would be looking at the number of clusters found and comparing membership similarity between like clusters. [Here](http://www.centerspace.net/clustering-analysis-part-iii-hierarchical-cluster-analysis) is a good overview of hierarchical clustering that my colleague wrote on clustering scotch whiskey's.
Take a look at [this](http://bioinfo.unice.fr/biodiv/Tree_editors.html) page that has lots of information about software that deals with trees, including dendrograms. I noticed several tools that deal with tree comparison, although I haven't personally used any of them yet. There are a number of references cited there also.