From: | Joshua N Pritikin <jpritikin(at)pobox(dot)com> |
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To: | hubert depesz lubaczewski <depesz(at)gmail(dot)com> |
Cc: | Oleg Bartunov <oleg(at)sai(dot)msu(dot)su>, pgsql-general(at)postgresql(dot)org |
Subject: | Re: tsearch2 questions |
Date: | 2007-07-04 09:16:47 |
Message-ID: | 20070704091647.GM25916@always.joy.eth.net |
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Lists: | pgsql-general |
On Wed, Jul 04, 2007 at 11:08:21AM +0200, hubert depesz lubaczewski wrote:
> On 7/4/07, Joshua N Pritikin <jpritikin(at)pobox(dot)com> wrote:
> >From where are you quoting? I was quoting from:
> >
> >http://www.sai.msu.su/~megera/postgres/gist/tsearch/V2/docs/tsearch2-ref.html
>
> i was quoting file
> http://www.sai.msu.su/~megera/postgres/gist/tsearch/V2/docs/tsearch-V2-intro.html
So that one is fine. Only the reference could use some clarification.
> >actually oleg supposed not to use best rank, but just use the formula as
> >> given - rank/(rank+1) to get rank in range of 0 to 1.
> >OK, then what does the +1 mean in your formulae? Consider these results
> >from [1]. rank/(rank+1): 0.19/.1 = 1.9, .1/.1 = 1, etc. That doesn't
> >make sense. The reciprocal also doesn't make sense. So what does Oleg
> >mean? I was guessing that Oleg meant to divide the rank column by the
> >first rank, that is, by 0.19 so you would get 1, .52, .52, etc.
>
> +1 means: add one to.
> for example: for rank = 0.1 you get: 0.1/(0.1+1) = 0.1/1.1 = 0.0909
> for rank = 0.5 you get: 0.5/(0.5+1) = 0.5/1.5 = 0.3333
D'oh! I see.
> i think that notation: rank+1 is pretty readable.
>
> additionally - sorry but i dont understand your calculations. what is
> 0.19/.1
> ? how did you get the .1?
I was imagining that "rank+1" was the second row of the rank column.
Sorry for the confusion.
--
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