% \VignetteIndexEntry{Weight-based deduplication}

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options(width=50)
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\documentclass[a4paper]{article}

\usepackage[ansinew]{inputenc}

\begin{document}

\title{Example session for Weight-based deduplication}
\author{Andreas Borg, Murat Sariyar}
\maketitle

This document shows an example session using the package 
\textit{RecordLinkage}. A single data set is deduplicated using an EM 
algorithm for weight calculation.
Conducting linkage of two data sets differs only in the step of generating
record pairs.

\section{Generating record pairs}

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library(RecordLinkage)
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The data to be deduplicated is expected to reside in a data frame or matrix,
each row containing one record. Example data sets of 500 and 10000 records
are included in the package as \texttt{RLData500} and \texttt{RLData10000}. 

<<>>=
data(RLdata500)
RLdata500[1:5,]
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For deduplication, \texttt{compare.dedup} is to be used. In this example,
blocking is set to return only record pairs which agree in at least two 
components of the subdivided date of birth, resulting in 810 pairs. 
The argument \texttt{identity} preserves the 
true matching status for later evaluation.

<<>>=
pairs=compare.dedup(RLdata500,identity=identity.RLdata500,blockfld=list(c(5,6),c(6,7),c(5,7)))
summary(pairs)
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\section{Weight calculation}

Weights are calculated by means of an EM algorithm. This step is computationally
intensive and might take a while.
The histogram shows the resulting weight distribution.
<<>>=
pairs=emWeights(pairs)
hist(pairs$Wdata, plot=FALSE)
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\section{Classification}

For determining thresholds, 
record pairs within a given range of weights can be printed using 
\texttt{getPairs}\footnote{The output of \texttt{getPairs} is shortened in this
document.}. In this case, $24$ is set as upper and $-7$ as lower threshold,
dividing links, possible links and non-links. The summary shows the resulting 
contingency table and error measures.


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getPairs(pairs,30,20)
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getPairs(pairs,30,20)[23:36,]
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pairs=emClassify(pairs, threshold.upper=24, threshold.lower=-7)
summary(pairs)
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Review of the record pairs denoted as possible links is facilitated by
\texttt{getPairs}, which can be forced to show only possible links via argument
\texttt{show}. A list with the ids of linked pairs can be extracted from the 
output of \texttt{getPairs} with argument \texttt{single.rows} set to 
\texttt{TRUE}.

<<>>=
possibles <- getPairs(pairs, show="possible")
possibles[1:6,]
links=getPairs(pairs,show="links", single.rows=TRUE)
link_ids <- links[, c("id1", "id2")]
link_ids

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\end{document}
