linkr_multi: Locally Optimal Linking Of Many Data Frames

In sumtxt/lychee: Optimal Linking and Joining of Data Frames in R

Description

Links a series of data frames sequentially: At each iteration, the function selects one element from all already matched tuples (found by linking data frame 1...d) and links it to the next data frame d+1 until no more data frames are available. All elements of a tuple are assigned the same identifier in the stacked data frame. Each tuple will include at most one element from every data frame d. The solution is a local approximation to the globally optimal solution.

Usage

linkr_multi(
  df,
  by,
  slice,
  strata = NULL,
  method = "osa",
  assignment = TRUE,
  na_matches = "na",
  pool = "last",
  caliper = Inf,
  C = 1,
  verbose = FALSE,
  ...
)

Arguments

df	data frame to link.
by	character vector of the key variable(s) to join by. To join by different variables on x and y, use a named vector. For example, by = c("a" = "b") will match x$a to y$b.
slice	used to split df into a list of data frames.
strata	character vector of variables to join exactly if any. Can be a named vector as for by.
method	the name of the distance metric to measure the similarity between the key columns.
assignment	should one-to-one assignments be constructed?
na_matches	should NA and NaN values match one another for any exact join defined by strata?
pool	one of four string values: "previous", "average", "last" or "random" (see details).
caliper	caliper value on the same scale as the distance matrix (before multipled by C).
C	scaling parameter for the distance matrix.
verbose	print distance summary statistic.
...	parameters passed to distance metric function.

Details

Splits df by slice into a list of data frames (indexed 1,...,d,...,D) and applies linkr to every element of this list. Each data frame d is linked to a pool of candidates. The candidate pool is defined by one observation from each matched tuple (which might only have a single element, i.e. a singleton) found in the data frames indexed 1...(d-1). By default, the last observation for each matched tuple is used (pool='last'). Other options to construct the candidate pool include:

• pool='random': pool includes a randomly drawn element from each matched tuple.

• pool='previous': pool includes all observations from the data frame indexed d-1.

• pool='average': pool includes a new observation with the average value per key variable for every matched tuple. This option will only work when the variable(s) defined by the parameter by are numeric.

For more details see the help file of linkr.

See Also

assignment linkr

Examples

library(dplyr)
data(greens3)

linkr_multi(
  df=filter(greens3, election=="BTW"), 
  by='city', 
  slice='year',
  method='lcs',
  caliper=15) %>% 
arrange(match_id,year) %>% 
 data.frame

sumtxt/lychee documentation built on July 15, 2020, 1:51 a.m.