A simple pass-through cache for complex or long running operations

executes expr and saves the output as an RDS file indexed by has of code in expr and the hash of input variables (which should contain any variable inputs)

Usage

cached(
  .expr,
  ...,
  .nocache = getOption("cache.disable", default = FALSE),
  .cache = getOption("cache.dir", default = rappdirs::user_cache_dir("ggrrr")),
  .prefix = getOption("cache.item.prefix", default = "cached"),
  .stale = getOption("cache.stale", default = Inf)
)

Arguments

.expr

the code the output of which requires caching. Other than a return value this should not create side effects or change global variables.

...

inputs that the code in expr depends on and changes in which require the code re-running, Could be Sys.Date()

.nocache

an option to defeat the caching which can be set globally as options("cache.disable"=TRUE)

.cache

the location of the cache as a directory. May get its value from options("cache.dir") or the default value of rappdirs::user_cache_dir("ggrrr")

.prefix

a name of the operation so that you can namespace the cached files and do selective clean up operations on them

.stale

the length of time in days to keep cached data before considering it as stale. can also be set by options("cache.stale")

Value

the output of .expr which will usually be a value

Examples

colName = "Petal.Width"
{
  iris[[colName]]
} %>% cached(iris, colName, .prefix="example", .cache=tempdir())
#> caching item: /tmp/Rtmp6208e5/example-4d33d39f25b44f2dd0e3f1c284e46470-7cbba346e54f9b12142893d1b0bc7858.rda
#>   [1] 0.2 0.2 0.2 0.2 0.2 0.4 0.3 0.2 0.2 0.1 0.2 0.2 0.1 0.1 0.2 0.4 0.4 0.3
#>  [19] 0.3 0.3 0.2 0.4 0.2 0.5 0.2 0.2 0.4 0.2 0.2 0.2 0.2 0.4 0.1 0.2 0.2 0.2
#>  [37] 0.2 0.1 0.2 0.2 0.3 0.3 0.2 0.6 0.4 0.3 0.2 0.2 0.2 0.2 1.4 1.5 1.5 1.3
#>  [55] 1.5 1.3 1.6 1.0 1.3 1.4 1.0 1.5 1.0 1.4 1.3 1.4 1.5 1.0 1.5 1.1 1.8 1.3
#>  [73] 1.5 1.2 1.3 1.4 1.4 1.7 1.5 1.0 1.1 1.0 1.2 1.6 1.5 1.6 1.5 1.3 1.3 1.3
#>  [91] 1.2 1.4 1.2 1.0 1.3 1.2 1.3 1.3 1.1 1.3 2.5 1.9 2.1 1.8 2.2 2.1 1.7 1.8
#> [109] 1.8 2.5 2.0 1.9 2.1 2.0 2.4 2.3 1.8 2.2 2.3 1.5 2.3 2.0 2.0 1.8 2.1 1.8
#> [127] 1.8 1.8 2.1 1.6 1.9 2.0 2.2 1.5 1.4 2.3 2.4 1.8 1.8 2.1 2.4 2.3 1.9 2.3
#> [145] 2.5 2.3 1.9 2.0 2.3 1.8
#> attr(,"cache-path")
#> [1] "/tmp/Rtmp6208e5/example-4d33d39f25b44f2dd0e3f1c284e46470-7cbba346e54f9b12142893d1b0bc7858.rda"
#> attr(,"cache-date")
#> [1] "2024-06-13 11:00:09 BST"