qdap (version 1.2.0)

lookup: Hash Table/Dictionary Lookup

Description

Environment based hash table useful for large vector lookups. terms %l% key.match - A binary operator version of lookup for when key.match is a data.frame or named list. terms %l+% key.match - A binary operator version of lookup for when key.match is a data.frame or named list and missing is assumed to be NULL.

Usage

lookup(terms, key.match, key.reassign = NULL, missing = NA)

terms %l% key.match

terms %l+% key.match

Arguments

terms

A vector of terms to undergo a lookup.

key.match

Takes one of the following: (1) a two column data.frame of a match key and reassignment column, (2) a named list of vectors (Note: if data.frame or named list supplied no key reassign needed) or (3) a single vector match key.

key.reassign

A single reassignment vector supplied if key.match is not a two column data.frame/named list.

missing

Value to assign to terms not matching the key.match. If set to NULL the original values in terms corresponding to the missing elements are retained.

Value

• Outputs A new vector with reassigned values.

See Also

new.env

Examples

## Supply a dataframe to key.match

lookup(1:5, data.frame(1:4, 11:14))

## Retain original values for missing
lookup(1:5, data.frame(1:4, 11:14), missing=NULL)

lookup(LETTERS[1:5], data.frame(LETTERS[1:5], 100:104))

key <- data.frame(x=1:2, y=c("A", "B"))
big.vec <- sample(1:2, 3000000, T)
out <- lookup(big.vec, key)
out[1:20]

## Supply a named list of vectors to key.match

codes <- list(A=c(1, 2, 4),
    B = c(3, 5),
    C = 7,
    D = c(6, 8:10))

lookup(1:10, codes)

## Supply a single vector to key.match and key.assign

lookup(mtcars$carb, sort(unique(mtcars$carb)),
    c('one', 'two', 'three', 'four', 'six', 'eight'))

lookup(mtcars$carb, sort(unique(mtcars$carb)),
    seq(10, 60, by=10))

## %l%, a binary operator version of lookup
1:5 %l% data.frame(1:4, 11:14)
1:10 %l% codes

1:12 %l% codes
1:12 %l+% codes