(This article was first published on

** bioCS**, and kindly contributed to

R-bloggers)
Coming from Python, the absence of a real dictionary in R has annoyed me for quite some time. Now, I actually needed to use vectors as keys in R:

library(dict)

d <- dict()

d[[1]] <- 42

d[[c(2, 3)]] <- "Hello!"

d[["foo"]] <- "bar"

d[[1]]

d[[c(2, 3)]]

d$get("not here", "default")

d$keys()

d$values()

d$items()

# [[ ]] gives an error for unknown keys

d[["?"]]

Under the hood, separate C++ dictionaries (unordered_map) are created for the different types of keys. Using R’s flexible types that are reflected in Rcpp (as SEXP), such a dictionary can store both numbers and strings (and other objects) at the same time.

The package is available on GitHub: https://github.com/mkuhn/dict

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