Perhaps this is what Jan had in mind: Tanimoto coefficient (extended Jaccard coefficient)
"Cosine similarity is a measure of similarity between two vectors of n dimensions by finding the angle between them, often used to compare documents in text mining." http://en.wikipedia.org/wiki/Jaccard_index -- David Mitchell On 12/20/2009 22:13, Henry Rich wrote: > Jan, > > I have looked for a description of Tanimoto distance but have not found > anything useful. Can you describe what it is or point to a description > of it? > > Henry Rich > > Jan Jacobs wrote: >> Henry, >> very good. For longer strings it is more than double so fast as the previous >> version. In my test cases it even consumes less memory. >> Is it possible to include this as a native function in J (e.g. overloading >> -. or s:)? >> Same question but now for Tanimoto distance? >> Jan. >> >> >> On 12/19/09, R.E. Boss<r.e.b...@planet.nl> wrote: >>> Smart analysis. Chapeau! >>> >>> >>> R.E. Boss >>> >>> >>> -----Oorspronkelijk bericht----- >>> Van: programming-boun...@jsoftware.com >>> [mailto:programming-boun...@jsoftware.com] Namens Henry Rich >>> Verzonden: zaterdag 19 december 2009 3:00 >>> Aan: Programming forum >>> Onderwerp: [Jprogramming] Levenshtein distance >>> >>> I was working with R. E.'s compact implementation of the Levenshtein >>> distance and I found an interesting equivalence: >>> >>> (<.>:)/\.&.|. >>> >>> can be replaced by >>> >>> (<./\@:- + ]) i...@# >>> >>> which uses a little more space but is quite a bit faster for large >>> operands. So now I have the version: >>> >>> NB. Levenshtein distance between two strings >>> levdist=: 4 : 0 >>> 'a b'=. (/: #&>)x;y >>> z=. i.>:#b >>> for_j. a do. >>> z=. ((<./\@:- + ]) i...@#) ((j ~: b) + }:z) ({...@] , (<. }.))>:z >>> end. >>> {:z >>> ) >>> >>> >>> Henry Rich >>> ---------------------------------------------------------------------- >>> For information about J forums see http://www.jsoftware.com/forums.htm >>> >>> ---------------------------------------------------------------------- >>> For information about J forums see http://www.jsoftware.com/forums.htm >>> >> >> >> > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
