Yes, that's really what I mean. ALS factors, among other things, a matrix of 1 where an interaction occurs and nothing (implicitly 0) everywhere else.
On Mon, May 6, 2013 at 9:40 PM, Tevfik Aytekin <tevfik.ayte...@gmail.com> wrote: > But the data under consideration here is not 0/1 data, it contains only 1's. > > On Mon, May 6, 2013 at 11:29 PM, Sean Owen <sro...@gmail.com> wrote: >> Parallel ALS is exactly an example of where you can use matrix >> factorization for "0/1" data. >> >> On Mon, May 6, 2013 at 9:22 PM, Tevfik Aytekin <tevfik.ayte...@gmail.com> >> wrote: >>> Hi Sean, >>> Isn't boolean preferences is supported in the context of memory-based >>> recommendation algorithms in Mahout? >>> Are there matrix factorization algorithms in Mahout which can work >>> with this kind of data (that is, the kind of data which consists of >>> users and the movies they have seen). >>> >>> >>> >>> >>> On Mon, May 6, 2013 at 10:34 PM, Sean Owen <sro...@gmail.com> wrote: >>>> Yes, it goes by the name 'boolean prefs' in the project since target >>>> variables don't have values -- they just exist or don't. >>>> So, yes it's certainly supported but the question here is how to >>>> evaluate the output. >>>> >>>> On Mon, May 6, 2013 at 8:29 PM, Tevfik Aytekin <tevfik.ayte...@gmail.com> >>>> wrote: >>>>> This problem is called one-class classification problem. In the domain >>>>> of collaborative filtering it is called one-class collaborative >>>>> filtering (since what you have are only positive preferences). You may >>>>> search the web with these key words to find papers providing >>>>> solutions. I'm not sure whether Mahout has algorithms for one-class >>>>> collaborative filtering. >>>>> >>>>> On Mon, May 6, 2013 at 1:42 PM, Sean Owen <sro...@gmail.com> wrote: >>>>>> ALS-WR weights the error on each term differently, so the average >>>>>> error doesn't really have meaning here, even if you are comparing the >>>>>> difference with "1". I think you will need to fall back to mean >>>>>> average precision or something. >>>>>> >>>>>> On Mon, May 6, 2013 at 11:24 AM, William <icswilliam2...@gmail.com> >>>>>> wrote: >>>>>>> Sean Owen <srowen <at> gmail.com> writes: >>>>>>> >>>>>>>> >>>>>>>> If you have no ratings, how are you using RMSE? this typically >>>>>>>> measures error in reconstructing ratings. >>>>>>>> I think you are probably measuring something meaningless. >>>>>>>> >>>>>>> >>>>>>> >>>>>>> I suppose the rate of seen movies are 1. Is it right? >>>>>>> If I use Collaborative Filtering with ALS-WR to get some >>>>>>> recommendations, I >>>>>>> must have a real rating-matrix? >>>>>>> >>>>>>> >>>>>>>
