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? >>>>>> >>>>>> >>>>>>
