Hello,


I've recently write down some measure for sets and now I wonder how it is called or where it is described?


The measure itself is the following:
Let $A$ & $B$ -- two sets of values from a single space (real line for example)
Let:


$d(A, B) = \sum\_{a \in A} \sum\_{b \in B} \frac{dist(a, b)}{len(A) \* len(B)}$


* $dist(a, b)$ is the distance between
two values
* $len(A)$ is the number of
the elements in $A$


So, the measure itself is:


$|| A, B || = \frac{d^2(A, B)}{|d(A, A) d(B, B)|} - 1$



How the distance between sets is called?
This seems related to cluster analysis, and your d(A, B) is used in "average linkage clustering."
<http://en.wikipedia.org/wiki/Cluster_analysis>


