In vgherard/r2r: R-Object to R-Object Hash Maps

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  fig.path = "man/figures/README-",
  out.width = "100%"
)

r2r

r2r provides a flexible implementation of hash tables in R, allowing for:

arbitrary R objects as keys and values,
arbitrary key comparison and hash functions,
customizable behaviour (throw or return a default value) on missing key exceptions.

Installation

You can install the released version of r2r from CRAN with:

install.packages("r2r")

and the development version from my R-universe repository, with:

install.packages("r2r", repos = "https://vgherard.r-universe.dev")

Usage

library(r2r)
m <- hashmap()

# Insert and query a single key-value pair
m[[ "user" ]] <- "vgherard"
m[[ "user" ]]

# Insert and query multiple key-value pairs
m[ c(1, 2, 3) ] <- c("one", "two", "three")
m[ c(1, 3) ]

# Keys and values can be arbitrary R objects
m[[ lm(mpg ~ wt, mtcars) ]] <- c(TRUE, FALSE, TRUE)
m[[ lm(mpg ~ wt, mtcars) ]]

Getting help

For further details, including an introductory vignette illustrating the features of r2r hash maps, you can consult the r2r website. If you encounter a bug, want to suggest a feature or need further help, you can open a GitHub issue.

Comparison with `hash`

CRAN package {hash} also offers an implementation of hash tables based on R environments. The two tables below offer a comparison between {r2r} and {hash} (for more details, see the benchmarks Vignette)

knitr::kable(
    data.frame(
        Feature = c(
            "Basic data structure",
            "Arbitrary type keys", 
            "Arbitrary type values",
            "Arbitrary hash function",
            "Arbitrary key comparison function",
            "Throw or return default on missing keys",
            "Hash table inversion"
        ),
        r2r = c("R environment", "X", "X", "X", "X", "X", ""),
        hash = c("R environment", "", "X", "", "", "", "X")
        ),
    align = "c",
    caption = "Features supported by {r2r} and {hash}."
    )

knitr::kable(
    data.frame(
        Task = c(
            "Key insertion",
            "Key query",
            "Key deletion"
            ),
        Comparison = c(
            "{r2r} ~ {hash}",
            "{r2r} < {hash}",
            "{r2r} << {hash}"
            )
        ),
    align = "c",
    caption = "Performances of {r2r} and {hash} for basic hash table operations."
    )