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.
If you have access to the underlying distance matrix that generated each dendrogram (you probably do if you generated the dendorograms in R), couldn't you just use correlation between the corresponding values of the two matrices? I know this doesn't address the letter of what you asked, but it's a good solution to the spirit of what you asked.