qs2 (version 0.2.1)

qs_cache: qcache

Description

Helper function for caching objects for long running tasks

Usage

qs_cache(
  expr,
  name,
  envir = parent.frame(),
  cache_dir = ".cache",
  clear = FALSE,
  prompt = TRUE,
  qs_save_params = list(),
  qs_read_params = list(),
  verbose = TRUE
)

Arguments

expr

The expression to evaluate.

name

The cached expression name (see details).

envir

The environment to evaluate expr in.

cache_dir

The directory to store cached files in.

clear

Set to TRUE to clear the cache (see details).

prompt

Whether to prompt before clearing.

qs_save_params

List of parameters passed on to qs_save.

qs_read_params

List of parameters passed on to qs_read.

verbose

Boolean. If TRUE, the function prints an informative message regarding the status of cached objects.

Details

This is a (very) simple helper function to cache results of long running calculations. There are other packages specializing in caching data that are more feature complete.

The evaluated expression is saved with qs_save() in <cache_dir>/<name>.qs2. If the file already exists instead, the expression is not evaluated and the cached result is read using qs_read() and returned.

To clear a cached result, you can manually delete the associated .qs2 file, or you can call qs_cache() with clear = TRUE. If prompt is also TRUE a prompt will be given asking you to confirm deletion. If name is not specified, all cached results in cache_dir will be removed.

Examples

cache_dir <- tempdir()

a <- 1
b <- 5

# not cached
result <- qs_cache({a + b},
                 name="aplusb",
                 cache_dir = cache_dir,
                 qs_save_params = list(compress_level = 5))

# cached
result <- qs_cache({a + b},
                 name="aplusb",
                 cache_dir = cache_dir,
                 qs_save_params = list(compress_level = 5))

# clear cached result
qs_cache(name="aplusb", clear=TRUE, prompt=FALSE, cache_dir = cache_dir)