rlist (version 0.3-2)

list.search: Search a list recusively by an expression

Description

Search a list recusively by an expression

Usage

list.search(.data, expr, classes = "ANY", n = Inf, unlist = FALSE)

Arguments

.data

list

expr

a lambda expression

classes

a character vector of class names that restrict the search. By default, the range is unrestricted (ANY).

n

the number of results to get

unlist

logical Should the result be unlisted?

Details

list.search evaluates an expression (expr) recursively along a list (.data). If the expression results in a single-valued logical vector and its value is TRUE, the whole vector will be collected If it results in multi-valued or non-logical vector, the non-NA values resulted from the expression will be collected. To search whole vectors that meet certain condition, specify the expression that returns a single logical value. To search the specific values within the vectors, use subsetting in the expression, that is, .[cond] or lambda expression like x -> x[cond] where cond is a logical vector used to select the elements in the vector.

Examples

# Exact search

x <- list(p1 = list(type="A",score=c(c1=9)),
       p2 = list(type=c("A","B"),score=c(c1=8,c2=9)),
       p3 = list(type=c("B","C"),score=c(c1=9,c2=7)),
       p4 = list(type=c("B","C"),score=c(c1=8,c2=NA)))

## Search exact values
list.search(x, equal("A", exactly = TRUE))
list.search(x, equal(c("A","B"), exactly = TRUE))
list.search(x, equal(c(9,7), exactly = TRUE))
list.search(x, equal(c(c1=9,c2=7), exactly = TRUE))

## Search all equal values
list.search(x, all(equal(9)))
list.search(x, all(equal(c(8,9))))
list.search(x, all(equal(c(8,9)),na.rm = TRUE))

## Search any equal values
list.search(x, any(equal(9)))
list.search(x, any(equal(c(8,9))))

## Search all/any included/excluded values
list.search(x, equal(9, include = TRUE))
list.search(x, all(equal(c(9,10), include = TRUE)))
list.search(x, any(equal(c(9,10), include = TRUE)))
list.search(x, all(!equal(c(7,9,10), include = TRUE)))

# Fuzzy search

data <- list(
  p1 = list(name="Ken",age=24),
  p2 = list(name="Kent",age=26),
  p3 = list(name="Sam",age=24),
  p4 = list(name="Keynes",age=30),
  p5 = list(name="Kwen",age=31)
)

list.search(data, equal("^K\\w+n$", pattern = TRUE), "character")

list.search(data, equal("Ken", dist = 1), "character")
list.search(data, equal("Man", dist = 2), "character")
list.search(data, !equal("Man", dist = 2), "character")

data <- list(
  p1 = list(name=c("Ken", "Ren"),age=24),
  p2 = list(name=c("Kent", "Potter"),age=26),
  p3 = list(name=c("Sam", "Lee"),age=24),
  p4 = list(name=c("Keynes", "Bond"),age=30),
  p5 = list(name=c("Kwen", "Hu"),age=31))

list.search(data, all(equal("Ken", dist = 1)), "character")
list.search(data, any(equal("Ken", dist = 1)), "character")
list.search(data, all(!equal("Ken", dist = 1)), "character")
list.search(data, any(!equal("Ken", dist = 1)), "character")

list.search(data, .[equal("e",pattern = TRUE)], "character")