Associated Array for R

Description Usage Arguments Details Value Author(s) See Also Examples

Functions for creating and working with hash objects:

Returns the number of items in a hash

hash(...)

is.hash(x)

## S3 method for class 'hash'
as.list(x, all.names = FALSE, ...)

## S4 method for signature 'hash'
length(x)

`...`	Additional arguments passed to the function #' HASH KEYS must be a valid character value and may not be the empty string `""`.
`x`	a hash object.
`all.names`	a logical indicating whether to copy all values or (default) only those whose names do not begin with a dot

hash Class constructor

is.hash test if object is of class "hash"

as.list

as.list.hash convert a hash object to a list

KEYS must be a valid R name, must be a character vector and must not be the empty string, "". When supplied by the used methods will try to coerce the keys to valid names using make_keys()

VALUES are restricted to any valid R objects. HASH VALUES can be any R value, vector or object.

codehash returns a hash object. Key-value pairs may be specified as:

explicitly named arguments keys and values
two unnamed objects of equal length as a set of key-value pairs
key=value pairs
a single naned vector
as a list

ACCESSORS. Hashes may be accessed via the standard R accessors [, [[ and \$. See hash::extract() for details.

PASS-BY REFERENCE. Environments and hashes are special objects in R because only one copy exists globally. When provided as an argument to a function, no local copy is made. When passes to functions, those functions can change the value of the hash. This is not typical of R.

PERFORMANCE. Hashes are based on R's native environments and are designed to be exceedingly fast using the environments internal hash table. For small data structures, a list will out-perform a hash in nearly every case. For larger data structure, i.e. > 500 key value pair the performance of the hash becomes faster. Much beyond that the performance of the hash far outperforms native lists.

Return the number of items in the hash by calling length() on the internal environment.

hash hash object

is.hash logical value indicating if the argument is a hash.

as.list list conversion from hash

length integer; number of key-value pairs in the hash

integer Number of items in the hash.

Christopher Brown

Christpher Brown

extract()

See Also hash(), length()

  hash()                            # empty 
  h <- hash()                       # associate a name to the hash 

  hash( new.env() )                 # from environment 
     
  hash( a=1, b=2, c=3 )             # key-value pairs using named arguments   
  
  hash( letters[1:3], 1:3 )         # unamed args: two equal length vectors 
  hash( letters[1:3], 1 )           # unamed args: all keys with same value
                                    
  hash( 1:3, lapply(1:3, seq, 1 ))  # same, arbitrary values
  
  hash( c(a=1, b=2, c=3) )          # named vector of key-value pairs
  hash( list(a=1,b=2,c=3) )         # named list of key-value pairs
 
  is.hash( hash() )
  as.list(h)   # CONVERT TO LIST



  h <- hash( letters, 1:26 )
  length(h) # 26