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From Ted Dunning <ted.dunn...@gmail.com>
Subject Re: SVD and Clustering
Date Mon, 05 Jul 2010 23:08:50 GMT
On Mon, Jul 5, 2010 at 12:34 PM, Grant Ingersoll <gsingers@apache.org>wrote:

>
> On Jul 5, 2010, at 1:17 PM, Ted Dunning wrote:
>
> > Yes to this.
> >
> > On Mon, Jul 5, 2010 at 6:43 AM, Grant Ingersoll <gsingers@apache.org>
> wrote:
> >
> >> is it just seen as a general way of doing feature reduction and
> therefore
> >> it makes sense to do.
>
> Should I normalize my vectors before doing SVD or after or not at all?


Yes.  :-)

Any of these can help.  Normalizing before will probably not have a huge
effect, but could be helpful if you have certain kinds of odd documents.
 Normalizing document vectors after SVD may be critical to avoid problems
with eigenspokes.  Avoiding normalization is important in certain other
situations.

So the answer to your two binary questions expressed as four possible
options is "Yes".

Try it and apply the laugh test to each option.

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