Displaying 4 results from an estimated 4 matches for "wdfn".
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2013 Mar 11
1
Implementation of the PL2 weighting scheme of the DFR Framework
...sampling or the risk gain (L) and within document frequency normalization
H2(2) (as proposed by Amati in his PHD thesis).
The formula for w(t,d) in this scheme is given by::-
w(t,d) = wqf * L * P
where
wqf = within query frequency
L = Laplace law of after effect sampling =1 / (wdfn + 1)
P = wdfn * log (wdfn / lamda) + (lamda - wdfn) log(e) + 0.5 * log
(2 * pi * wdfn)
wdfn = wdf * (1+c * log(average length of document in database /
length of document d )) (H2 Normalization )
lamda = mean of the Poisson distrubution = Collection frequency of
the term...
2013 Feb 19
2
Implementing tf-idf weighting scheme in Xapian
...the wdf (within
document frequency) ,then an upper bound on W(t,d) will be
(log(wdf_upperbound_)+1)*log(N/termfreq) as N(collection size) and
termfreq(number of documents indexed by the term t) will remain constant
for a given term t.
However,some normalizations for the wdf include the formula wdfn = wdf /
max(wdf,d) where max(wdf,d) is the maximum within document frequency of any
term in the document .This metric is not provided by the need_stat( )
function of the Xapian::Weight class and so I don't know how to procure
it.Please can someone help me that ?
I will work on implementing wei...
2016 Jul 28
2
Weighting Schemes: Evaluation results
Ah. If FIRE doesn't have something that can show this suitably, then
> maybe Parth can advise on access to TREC, as I know he's used some of
> them in the past.
>
?I can say FIRE is also a reliable source but INEX/TREC are better. INEX
can give you free access and TREC is not freely available. I had used INEX
for xapian in the past and some details are here:
2016 Aug 07
2
Weighting Schemes: Evaluation results
Hi,
Evaluation of pivoted normalization ("PPP") of tf-idf weighting scheme is
also complete now. I have also evaluated the default tf-idf normalization
("ntn") and other normalizations combinations involving pivoted
normalization in wdfn, idfn and wtn component as "Pxx", "xPx" and "xxP"
normalization strings respectively to have a clear idea about which one
does better job of retrieving relevant documents.
All results of evaluation runs can be easily accessed here:
https://gist.github.com/ivmarkp
Com...