mahout-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From michal shmueli <>
Subject Re: problems with GenericRecommenderIRStatsEvaluator:
Date Thu, 05 Nov 2009 13:08:11 GMT
The way i envision this is the follow: assume user rates 10 items, this 10
are the correct items. Further assume that for recommendation we use subset
of this 10 items, say 70% (leave us with 30% for test) to build the
similarity, etc. Now, during evaluation, we ask from the recommneder for say
k items, and we check how many from the 3 correct item (the 30% of the
tests) are within the k recommended items.
This solutions ignore the ranking on the different items, however, this
could be also added later.

Does it make sense?


On Thu, Nov 5, 2009 at 2:16 PM, Sean Owen <> wrote:

> It doesn't simulate "training" and "test", that's what I'm saying.
> This concept exists in RecommenderEvaluator, not
> RecommenderIRStatsEvaluator. They're reasonably different things.
> In RecommenderIRStatsEvaluator, there is instead a "relevance
> threshold" parameter.
> But the final parameter, which you refer to, is something else still.
> It simply controls what percentage of all data to use. It's a simple
> way to use a lot less data to produce a result faster.
> You are right that in your 'boolean' data, all preference values are
> effectively 1.0. So passing a 1.0 means that all items are considered
> relevant. That's fine, that's reasonable. While the framework
> typically removes all relevant items from a user for test purposes, it
> will remove only up to "at" items -- that is, if you are evaluating
> precision at 5, it will remove up to 5 items. In this case they are
> effectively randomly chosen since all items are equal.
> How would you like it to choose the relevant and not relevant items in
> this case? we can figure out how to do it then.
> Sean
> On Thu, Nov 5, 2009 at 12:06 PM, michal shmueli
> <> wrote:
> >    >>  I still don't get why this parameter simulates the "training" and
> > the "test". In addition, since my data is Boolean, ain't it mean that
> anyway
> > what is 1 is relevant ? Is there another way to tell the recommender how
> to
> > chose the training and test sets?

  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message