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From Lance Norskog <goks...@gmail.com>
Subject Re: [jira] Commented: (MAHOUT-558) Extend ItembasedRecommender to offer different "exclusion modes" when computing most similar items to a collection of input items
Date Mon, 06 Dec 2010 23:09:48 GMT
I'm working on User-Item and Item-Item Recommenders based on Semantic Vectors:

http://ultrawhizbang.blogspot.com/2010/11/semantic-vectors-part-1.html
http://ultrawhizbang.blogspot.com/2010/11/semantic-vectors-for-recommenders-with.html

(Please comment on errors and lack of clarity.)

The SemanticVectorDataModel only saves the projected vectors, not the
original recommender input. It cannot return the original prefs, only
its own prefs (N-dimensional vector distances).

On Mon, Dec 6, 2010 at 1:53 AM, Sean Owen (JIRA) <jira@apache.org> wrote:
>
>    [ https://issues.apache.org/jira/browse/MAHOUT-558?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12967140#action_12967140
]
>
> Sean Owen commented on MAHOUT-558:
> ----------------------------------
>
> There's a tension between the need to fit several algorithms into one common API, and
the fact that they do have different characteristics. Making them all work exactly the same
would mean jumping through a few hoops and also cutting off access to shortcuts that improve
performance.
>
> One big example to me is fudging what a preference estimate means when the data model
has no preference values. estimatePreference() should unusefully return 1.0 all the time,
really but it doesn't, in order to be more useful in practice.
>
> That said, at the level of your example we ought to have consistent behavior. Which recommender
doesn't return the known pref value? That sounds like an unintentional behavior.
>
> However I would point out that the contract is to "estimate" a preference -- nobody said
what the estimate has to be!
>
>> Extend ItembasedRecommender to offer different "exclusion modes" when computing most
similar items to a collection of input items
>> ---------------------------------------------------------------------------------------------------------------------------------
>>
>>                 Key: MAHOUT-558
>>                 URL: https://issues.apache.org/jira/browse/MAHOUT-558
>>             Project: Mahout
>>          Issue Type: New Feature
>>          Components: Collaborative Filtering
>>    Affects Versions: 0.5
>>            Reporter: Sebastian Schelter
>>         Attachments: MAHOUT-558-2.patch, MAHOUT-558.patch
>>
>>
>> GenericItembased Recommender currently excludes all items that are not similar at
least one of the input items when computing the most similar items to a collection of items.
We should introduce a way to have the user decide whether he/she wants this behavior or he/she
wants to have all items included that are similar to at least one of the input items, which
is more useful in practice in my experience.
>
> --
> This message is automatically generated by JIRA.
> -
> You can reply to this email to add a comment to the issue online.
>
>



-- 
Lance Norskog
goksron@gmail.com

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