match.tbl: Match Table
In rBatt/trawlData: Read and Clean Data from Bottom Trawl Surveys

Description Usage Arguments Details Value Warning Examples

Find (via potentially fuzzy matching) values in a table given a lookup reference

1 2	## S3 method for class 'tbl' match(ref, tbl.ref, tbl.val, exact = FALSE)

`ref`	a vector of reference values to lookup
`tbl.ref`	reference values in the table to be matched to `ref`
`tbl.val`	values to be retrieved from the table when found in association with `tbl.ref`
`exact`	logical, default FALSE; if TRUE, matches of `ref` to `tbl.ref` needn't be exact

When exact=FALSE, match.tbl performs a match, with the added utility of returning a value in the table (rather than simply the index of the matches). When exact=TRUE, functions in cull are called to reformat ref and search for a match. If not match is found still, then fuzzy matching is performed via agrep on versions of ref that have and have not been formatted via cull.

The values of val.src indicate the amount of fuzziness involved in the match:

m1	an exact match
m2	exact match after `cull`
m3	fuzzy match performed on ref
m4	fuzzy match performed on `cull(ref)`

Fuzzy matching performed with agrep, with arguments ignore.case=TRUE, max.distance=0.25.

A data.table with 4 columns:

[,1]	ref	`class(ref)`	the reference value
[,2]	val	`class(val)`	the value from the table (usually this is the desired output)
[,3]	val.src	character	the source of the match
[,4]	tbl.row	integer	Row of match in the table

I am suspicous that the values returned in tbl.ref may be inaccurate. However, this quality, and the function in general, has not been thoroughly tested. Although use-cases have given desirable results, albeit I think that the fuzzy matching can be a bit too fuzzy (finding matches where there shouldn't be any). Be aware.

library(data.table)
tbl <- data.table(animal=c(
	"cats",
	"dogs",
	"elephant",
	"giraffe",
	"monkey",
	"person",
	"Gadus morhua",
	"Paralichthys dentatus",
	"Pomatomus saltatrix",
	"Amphiprioninae"
), a=1:10, b=10:1)
ref <- c(
	"GADUS MORHUA",
	"Amphiprion (the computer)",
	"elehpant",
	"dogs",
	"squirrel",
	"gaus"
)
tbl.ref <- tbl[,animal]
match.tbl(ref, tbl.ref, tbl[,animal]) # return what was matched to
match.tbl(ref, tbl.ref, tbl[,a]) # return another column