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From Ted Dunning <ted.dunn...@gmail.com>
Subject Re: Question about Pearson Correlation in non-Taste mode
Date Sat, 30 Nov 2013 06:34:46 GMT
On Fri, Nov 29, 2013 at 10:16 PM, Amit Nithian <anithian@gmail.com> wrote:

> Hi Ted,
>
> Thanks for your response. I thought that the mean of a sparse vector is
> simply the mean of the "defined" elements? Why would the vectors become
> dense unless you're meaning that all the undefined elements (0?) now will
> be (0-m_x)?
>

Yes.  Just so.  All those zero elements become non-zero and the vector is
thus non-dense.


>
> Looking at the following example:
> X = [5 - 4] and Y= [4 5 2].
>
> is m_x 4.5 or 3?


3.

This is because the elements of X are really 5, 0, and 4.  The zero is just
not stored, but it still is the value of that element.


> Is m_y 11/3 or (6/2) because we ignore the "5" since it's
> counterpart in X is undefined?.
>

11/3

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