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From Lance Norskog <goks...@gmail.com>
Subject Re: Using SVD-conditioned matrix
Date Mon, 17 Sep 2012 09:20:47 GMT
Thanks- I will mess around in R with this advice.

On Mon, Sep 17, 2012 at 12:30 AM, Sean Owen <srowen@gmail.com> wrote:
> On Mon, Sep 17, 2012 at 12:11 AM, Ted Dunning <ted.dunning@gmail.com> wrote:
>
>>   A_k = U_k U_k' A_k
>
>> Forgetting S_k is a bit dangerous here.  It is true that
>>
>>     U_k S_k = A_k V_k
>>
>> But, of course, right multiplying by V_k' gives us the identity above.
>>
>> I think that the real confusion is that I am talking about projecting back
>> into span A and you are talking about expressing things in terms of the
>> latent variables.
>
> Right, this goes all the way to "making recommendations", back to Ak.
> I think Lance was asking about how to find the new row in latent
> feature space, a row in Uk.
>
> You can't ignore Sk, yes, just trying to get to the essence. Putting
> it back in (half-and-half) does get what I posted which indeed is the
> project I think that was in question..
>
> Uk * sqrt(Sk) = Ak * Vk * 1/sqrt(Sk)



-- 
Lance Norskog
goksron@gmail.com

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