# Example session for Weight-based deduplication

#### Andreas Borg, Murat Sariyar

This document shows an example session using the package 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.

## Generating record pairs

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 `RLData500` and `RLData10000`.

    data(RLdata500)
    RLdata500[1:5,]

    ##   fname_c1 fname_c2 lname_c1 lname_c2   by bm bd
    ## 1  CARSTEN     <NA>    MEIER     <NA> 1949  7 22
    ## 2     GERD     <NA>    BAUER     <NA> 1968  7 27
    ## 3   ROBERT     <NA> HARTMANN     <NA> 1930  4 30
    ## 4   STEFAN     <NA>    WOLFF     <NA> 1957  9  2
    ## 5     RALF     <NA>  KRUEGER     <NA> 1966  1 13

For deduplication, `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 `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)

    ##
    ## Deduplication Data Set
    ##
    ## 500 records
    ## 571 record pairs
    ##
    ## 49 matches
    ## 522 non-matches
    ## 0 pairs with unknown status

## 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)

    ## $breaks
    ##  [1] -15 -10  -5   0   5  10  15  20  25  30  35  40  45
    ##
    ## $counts
    ##  [1] 352  13   0   0   5  26  42 123   9   0   0   1
    ##
    ## $density
    ##  [1] 0.1232924694 0.0045534151 0.0000000000 0.0000000000
    ##  [5] 0.0017513135 0.0091068301 0.0147110333 0.0430823117
    ##  [9] 0.0031523643 0.0000000000 0.0000000000 0.0003502627
    ##
    ## $mids
    ##  [1] -12.5  -7.5  -2.5   2.5   7.5  12.5  17.5  22.5  27.5
    ## [10]  32.5  37.5  42.5
    ##
    ## $xname
    ## [1] "pairs$Wdata"
    ##
    ## $equidist
    ## [1] TRUE
    ##
    ## attr(,"class")
    ## [1] "histogram"

## Classification

For determining thresholds, record pairs within a given range of weights can be printed using `getPairs` 1. 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.

    getPairs(pairs, 30, 20)

    ##     id fname_c1 fname_c2 lname_c1 lname_c2   by bm bd
    ## 23 457   URSULA   BIRGIT  MUELLER     <NA> 1940  6 15
    ## 24
    ## 25 467   ULRIKE   NICOLE   BECKRR     <NA> 1982  8  4
    ## 26 472   ULRIKE   NICOLE   BECKER     <NA> 1982  8  4
    ## 27
    ## 28 183   ULRICH     <NA>  MUELLER     <NA> 1962  6 19
    ## 29 444    SILKE     <NA>  MUELLER     <NA> 1962  6 14
    ## 30
    ## 31  25 MATTHIAS     <NA>     HAAS     <NA> 1955  7  8
    ## 32 107 MATTHIAS     <NA>     HAAS     <NA> 1955  8  8
    ## 33
    ## 34 106    ANDRE     <NA>  MUELLER     <NA> 1976  2 25
    ## 35 175    ANDRE     <NA>  MUELLER     <NA> 1976  1 25
    ## 36
    ##      Weight
    ## 23 25.14137
    ## 24
    ## 25
    ## 26 25.14137
    ## 27
    ## 28
    ## 29 24.20333
    ## 30
    ## 31
    ## 32 24.11923
    ## 33
    ## 34
    ## 35 24.11923
    ## 36

    pairs <- emClassify(pairs, threshold.upper = 24, threshold.lower = -7)
    summary(pairs)

    ##
    ## Deduplication Data Set
    ##
    ## 500 records
    ## 571 record pairs
    ##
    ## 49 matches
    ## 522 non-matches
    ## 0 pairs with unknown status
    ##
    ##
    ## Weight distribution:
    ##
    ## [-15,-10]  (-10,-5]    (-5,0]     (0,5]    (5,10]   (10,15]
    ##       352        13         0         0         5        26
    ##   (15,20]   (20,25]   (25,30]   (30,35]   (35,40]   (40,45]
    ##        42       123         9         0         0         1
    ##
    ## 15 links detected
    ## 198 possible links detected
    ## 358 non-links detected
    ##
    ## alpha error: 0.000000
    ## beta error: 0.002786
    ## accuracy: 0.997319
    ##
    ##
    ## Classification table:
    ##
    ##            classification
    ## true status   N   P   L
    ##       FALSE 358 163   1
    ##       TRUE    0  35  14

Review of the record pairs denoted as possible links is facilitated by `getPairs`, which can be forced to show only possible links via argument `show`. A list with the ids of linked pairs can be extracted from the output of `getPairs` with argument `single.rows` set to `TRUE`.

    possibles <- getPairs(pairs, show = "possible")
    possibles[1:6,]

    ##    id  fname_c1 fname_c2 lname_c1 lname_c2   by bm bd
    ## 1  17 ALEXANDER     <NA>  MUELLER     <NA> 1974  9  9
    ## 2 193 CHRISTIAN     <NA>  MUELLER     <NA> 1974  8  9
    ## 3
    ## 4  61     ANDRE     <NA>  FISCHER     <NA> 1943  6 25
    ## 5 254  STEFANIE     <NA>  FISCHER     <NA> 1943 11 25
    ## 6
    ##      Weight
    ## 1
    ## 2 21.691086
    ## 3
    ## 4
    ## 5 21.691086
    ## 6

    links <- getPairs(pairs, show = "links", single.rows = TRUE)
    link_ids <- links[, c("id1", "id2")]
    link_ids

    ##     id1 id2
    ## 290 290 466
    ## 50   50 234
    ## 87   87 117
    ## 145 145 240
    ## 286 286 383
    ## 289 289 399
    ## 297 297 388
    ## 357 357 414
    ## 313 313 457
    ## 467 467 472
    ## 183 183 444
    ## 25   25 107
    ## 106 106 175
    ## 370 370 478
    ## 127 127 142

1. The output of `getPairs` is shortened in this document.↩︎