Is There a Dictionary Functionality in R

Question

Is there a way to create a "dictionary" in R, such that it has pairs? Something to the effect of:

x=dictionary(c("Hi","Why","water") , c(1,5,4))
x["Why"]=5

I'm asking this because I am actually looking for a two categorial variables function.

So that if x=dictionary(c("a","b"),c(5,2))

     x  val
1    a  5 
2    b  2

I want to compute x1^2+x2 on all combinations of x keys

     x1 x2 val1  val2  x1^2+x2
1    a  a   5     5      30
2    b  a   2     5      9
3    a  b   5     2      27
4    b  b   2     2      6

And then I want to be able to retrieve the result using x1 and x2. Something to the effect of: get_result["b","a"] = 9

what is the best, efficient way to do this?

Accepted Answer

I know three R packages for dictionaries: hash, hashmap, and dict.

Update July 2018: a new one, container.

Update September 2018: a new one, collections

Must Read

hash

Keys must be character strings. A value can be any R object.

library(hash)
## hash-2.2.6 provided by Decision Patterns
h <- hash() 
# set values
h[["1"]] <- 42
h[["foo"]] <- "bar"
h[["4"]] <- list(a=1, b=2)
# get values
h[["1"]]
## [1] 42
h[["4"]]
## $a
## [1] 1
## 
## $b
## [1] 2
h[c("1", "foo")]
## <hash> containing 2 key-value pair(s).
##   1 : 42
##   foo : bar
h[["key not here"]]
## NULL

To get keys:

keys(h)
## [1] "1"   "4"   "foo"

To get values:

values(h)
## $`1`
## [1] 42
## 
## $`4`
## $`4`$a
## [1] 1
## 
## $`4`$b
## [1] 2
## 
## 
## $foo
## [1] "bar"

The print instance:

h
## <hash> containing 3 key-value pair(s).
##   1 : 42
##   4 : 1 2
##   foo : bar

The values function accepts the arguments of sapply:

values(h, USE.NAMES=FALSE)
## [[1]]
## [1] 42
## 
## [[2]]
## [[2]]$a
## [1] 1
## 
## [[2]]$b
## [1] 2
## 
## 
## [[3]]
## [1] "bar"
values(h, keys="4")
##   4
## a 1
## b 2
values(h, keys="4", simplify=FALSE)
## $`4`
## $`4`$a
## [1] 1
## 
## $`4`$b
## [1] 2

Is There a Dictionary Functionality in R

6 Answers

Must Read

hash

Chloe Bennett