♻️ cache: easily cache and retrieve computation results

The cache package provides a simple interface to caching which works across interactive R sessions, R scripts and Rmarkdown documents. Simply wrap your R expressions with the cache() function to cache or retrieve the results:

cache(resultOf = longComputation())

Installation

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

install.packages("cache")

and the development version from GitHub with:

if (!require(devtools)) install.packages("devtools")
devtools::install_github("OlivierBinette/cache")

Examples

Overview

Wrap any R expression using the cache() function to cache the result:

library(cache)

cache(myComputation = {Sys.sleep(3); "Hello World"})

The variable named myComputation contains the result of the computation and is available in your environment:

print(myComputation)
#> [1] "Hello World"

While it takes 3 seconds to evaluate the expression {Sys.sleep(3); "Hello World"}, the previously cached result can be instantly retrieved using the same function call:

system.time(
  cache(myComputation = {Sys.sleep(3); "Hello World"})
)
#>    user  system elapsed 
#>   0.001   0.000   0.002

print(myComputation)
#> [1] "Hello World"

This is especially useful as part of a reproducible analysis workflow or as part of an Rmarkdown document. However, in constrast with the cache functionality of the rmarkdown package, the cache package can be used seamlessly across interactive sessions, reproducible analyses and Rmarkdown knitting.

Specify cache directory

No two objects of the same name can be placed in the same cache directory. Analysis-specific cache directory should therefore be used when conflicts are expected. We recommend using the here() function from the here package to specify cache file paths relatively to the project root:

cache(.cachedir = here::here(".cache-R/cars-analysis"),
  result = lm(cars)
)

Clear cache and re-run expressions

Use the .rerun argument to clear cache and rerun expressions:

cache(.rerun=TRUE,
  myComputation = {Sys.sleep(3); "Hello World"}
)

Load cached objects

Cached objects can also be loaded directly using the cache_load() function:

# Load all cached objects from the `.cache-R` directory
cache_load()
#> ℹ Reading the following objects from cache:  myComputation

# Load specific object
cache_load("myComputation")
#> ℹ Reading the following objects from cache:  myComputation

Notes

By default, the cache directory is located under a ./cache-R folder created at the root of your project directory. This folder is located using the here::here() function to ensure that all project files and documents can locate it as needed.

To clear the cache and rerun all expressions, either delete the .cache-R folder or supply the argument .rerun = FALSE to the cache() function calls.

References

• Cook, J. (2020) Caching in R. https://www.r-bloggers.com/2020/04/caching-in-r/