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From charlysf <charles.rue...@gmail.com>
Subject Re: Questions about PearsonCorrelation on a example
Date Tue, 23 Jun 2009 22:43:51 GMT

Of course, thank you very much, it's because now my table is almost empty, in
this case, do you recommend to me to use an other similarity ?


srowen wrote:
> 
> It doesn't have to do with the mean preference value being 0.
> 
> The problem is that these users overlap in only one item, and so,
> Pearson cannot compute a similarity since it cannot define a
> correlation coefficient. A correlation would require at least two data
> points. Add some more data and you will get non-NaN values.
> 
> On Tue, Jun 23, 2009 at 6:38 PM, charlysf<charles.ruelle@gmail.com> wrote:
>>
>> Hello,
>>
>> I use PearsonCorrelation, and I would like to understand why on my
>> example,
>> I have a NaN.
>> http://www.nabble.com/file/p24175732/Image%2B3.png
>>
>> http://www.nabble.com/file/p24175732/Image%2B4.png
>>
>>
>> I use PearsonCorrelation for an Item Basis recommender, and I of course
>> expect, to have a similarity between the two items, because they are
>> linked
>> to a same user.
>>
>> But in fact, I have a NaN.
>>
>> I saw that the mean of the data should be 0, but or me, 0 is the neutral
>> score, and I can't be sure that for each user, their mean is 0, is it
>> important ? I don't really understand why.
>>
>>
>> Thank you.
>> --
>> View this message in context:
>> http://www.nabble.com/Questions-about-PearsonCorrelation-on-a-example-tp24175732p24175732.html
>> Sent from the Mahout User List mailing list archive at Nabble.com.
>>
> 
> 

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View this message in context: http://www.nabble.com/Questions-about-PearsonCorrelation-on-a-example-tp24175732p24175800.html
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