extract: Extract

In decisionpatterns/r-hash: A Hash/Dictionary/Map/Associated Array for R

Description

These are the hash accessor methods. They closely follow the R style.

Usage

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

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

## S4 replacement method for signature 'hash,ANY,missing,ANY'
x[i, j, ...] <- value

## S4 replacement method for signature 'hash,ANY,missing,'NULL''
x[i, j, ...] <- value

## S4 replacement method for signature 'hash,'NULL''
x$name <- value

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

## S4 replacement method for signature 'hash,ANY,missing,'NULL''
x[[i]] <- value

Arguments

x	hash() object
i	keys to get or set
j	unused; retained to be compatoble with base package
...	Arguments passed to additional methods sapply()
drop	unused; retained to be compatible with base package
value	the value to set for the key-value pair
name	the key name $ is a look-up operator for a single key. The base $ method are used directly on the inherited environment. The supplied key is taken as a string literal and is not interpreted. The replaement form, $<- mutates the hash in place. [[ is the look-up, extraction operator. It returns the value of a single key and will interpret its argument. The replacement method, [[<- mutates the hash in place. [ is a slice operator. It returns a hash with the subset of key-value pairs. Unlike the other accessor methods, [ returns a copy. All hash key misses return NULL. All hash key replacements with NULL delete the key-value pair from the hash. $ and [[ return the value for the supplied argument. If i is not a key of x, NULL is returned with a warning. [ returns a hash slice, a subhash copy x with only the keys i defined. See details above for the complete explanation.

Author(s)

Christopher Brown

See Also

• del() for removing keys

• clear() for removing all keys

• keys() to get/set/rename keys

• values() to get/set/edit values

• hash()

Examples

  h <- hash( c('a','b','c'), 1:3 )

  # NAMED ACCESS
  
  h$a  # 1
  h$c  # 3
  
  # class of values change automatically
  class(h$a)  # integer
  h$a <- 1.1 
  class(h$a)  # numeric
  
  # values can contain more complex objects
  h$a <- 1:6
  h

  h$a <- NULL  # DELETE key 'a', will return null
  
  
  # INTERPRETED ACCESS
  
  h[[ "a" ]] <-"foo"    # Assigns letters, a vector to "foo"
  nm = "a"
  
  # SLICE ACCESS
  h[ nm ] <- "bar"   # h$a == bar
  h[ nm ] <- NULL
  
  
  # Slice 
  h[ keys(h) ]
  h[ keys(h) ] <- list( 1:2, 1:3 )
  h

decisionpatterns/r-hash documentation built on Feb. 6, 2019, 10:27 p.m.