extract: Extraction operators for Searchable object

In decisionpatterns/searchable: Customize Search/Slice/Subset Behavior for Accessing Subsets of List, Vectors, Environments, Hashes and Other R Objects

Description

Defines [, [[, and $ for Searchable objects

Usage

## S4 method for signature 'Searchable,PatternOrCharacter,missing'
x[i, j, ..., drop = TRUE]

## S4 replacement method for signature 'Searchable,character,missing'
x[i] <- value

Arguments

x	Searchable object
i	character; pattern with potential match modifiers applied,
j	missing; never specified
...	additional arguments. See Extract
drop	For matrices and arrays. If TRUE the result is coerced to the lowest possible dimension (see the examples). This only works for extracting elements, not for the replacement. See drop for further details.
value	replacement value for replacement functions The methods for searching respect the modifiers applied to both x and i.

Value

The values after the extracting methods have been applied:
\[ returns a subset of x, but which is not Searchable.
\[\[ and \$ return a sinlge element of x

[, [<-

[ and [<- are used for subsetting and replacing zero or more elemenxts of x. Used with searchable objects, these operators differ from normal R operations in the following respects:

• The search returns elements of the target that matches ANY of the search patterns.

• Unlike the its normal behavior, \[ does not guarantee the output to have as many elements as elements to pattern.

• [ does not return a Searchable object. It is thought that the return valuable will not be subsequently searched. It is easy to turn the results into a Searchable object using searchable however.

• Unlike for environments and hashes, no constraints exist for ensuring uniqueness for names in vectors and lists. These structures may contain multiple elements with the same name. Normal attempts to extract by name yield only the first element that matches the name. Using a Searchable patterns match yields all matching elements.

See Also

Searchable
Extract
Match mofiers: fixed, regex, coll and ignore.case reverse.lookup

Examples

# ATOMIC VECTORS:
    v <- c( a=1, b=2, B=3, c=4, c2=5 )
    sv <- searchable(v)


  # FLEXIBLY FIND ELEMENTS BY NAME
    sv[ regex('c') ]
    sv[ fixed('c') ]

    sv[ ignore.case('b') ]


  # FLEXIBLY REPLACEMENT ELEMENTS BY NAME
    sv[ regex('c.?') ]   <- "3rd"


  # SET DEFAULT SEARCH FOR TARGET/OBJECT
    sv <- searchable(v, case_insensitive = TRUE )
    sv['b']
    sv['B']

    sv <- regex(sv)
    sv['c']

    sv <- ignore.case(sv)
    sv['b']
    sv['c']                  # st


  # USE ON (RECURSIVE) LISTS:
    l <- list( a=1, b=2, c=3 )
    sl <- searchable(l)
    sl["b"]
    sl[ ignore.case("B") ]


  # USE WITH MAGRITTR
   ## Not run: 
    sl[ "B"  %>% ignore.case ]
    "b" %>% sl[.]
    "B" %>% ignore.case %>% sl[.]
   
## End(Not run)

decisionpatterns/searchable documentation built on Jan. 8, 2019, 3:28 a.m.