Are there any measures of self-similarity? On Sun, Jul 8, 2012 at 6:07 PM, Ted Dunning <[email protected]> wrote:
> I can't comment on the existing evaluators, but for me the only real > measure that I care about is average distance to nearest cluster for new or > held-out data. I will be building something of this sort for the > clustering part of the knn code I have been working on. > > > On Sun, Jul 8, 2012 at 5:44 PM, Pat Ferrel <[email protected]> wrote: > >> To use something like kmeans on any large and changing data set it seems >> a requirement that there be some means of evaluating the quality of >> clusters at different scales. The usual eyeballing breaks down quickly. >> >> Trying to use the cluster evaluators in Mahout with kmeans as the >> clustering method and cosine and the distance measure has proven >> problematic. The method is to iterate through the data using different ks >> and performing the evaluation at each point. What I find is that certain >> values are almost always in error. The Intra-cluster density from >> ClusterEvaluator is almost always NaN. The CDbw inter-cluster density is >> almost always 0. I have also seen several cases where CDbw fails to return >> any results but have not tracked down why yet. >> >> Given that the data for either evaluator is usually incomplete these >> methods are not very useful. Is mahout dropping the evaluators? Is the >> general wisdom that they are not particularly useful? Should a newer method >> be pursued? This seems a fairly important question to me, am I missing >> something? >> >> Raw data for a sample crawl is given below: >> >> >> >> > -- Lance Norskog [email protected]
