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 (0m_x)?
>
Yes. Just so. All those zero elements become nonzero and the vector is
thus nondense.
>
> 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
