loadCache {R.cache}R Documentation

Loads data from file cache

Description

Loads data from file cache, which is unique for an optional key object.

Usage

## Default S3 method:
loadCache(key=NULL, sources=NULL, suffix=".Rcache", removeOldCache=TRUE, pathname=NULL, dirs=NULL, ...)

Arguments

key An optional object from which a hexadecimal hash code will be generated and appended to the filename.
sources Optional source objects. If the cache object has a timestamp older than one of the source objects, it will be ignored and removed.
suffix A character string to be appended to the end of the filename.
removeOldCache If TRUE and the cache is older than the sources, the cache file is removed, otherwise not.
pathname The pathname to the cache file. If specified, arguments key and suffix are ignored. Note that this is only needed in order to read a cache file for which the key is unknown, for instance, in order to investigate an unknown cache file.
dirs A character vector constituting the path to the cache subdirectory to be used. If NULL, the root path is used.
... Additional argument passed to load().

Details

The hash code calculated from the key object is a 32 characters long hexadecimal MD5 hash code. For more details, see the digest package.

Value

Returns an R object or NULL, if cache does not exist.

Requirements

To make use of the key argument, the digest package (available on CRAN) must be installed, otherwise an error is generated. That package is not required when key==NULL.

Author(s)

Henrik Bengtsson (http://www.braju.com/R/)

See Also

saveCache(). The cache method in Bioconductor.

Examples

simulate <- function(mean, sd) {
  # 1. Try to load cached data, if already generated
  key <- list(mean, sd)
  data <- loadCache(key)
  if (!is.null(data)) {
    cat("Loaded cached data\n")
    return(data);
  }

  # 2. If not available, generate it.
  cat("Generating data from scratch...")
  data <- rnorm(1000, mean=mean, sd=sd)
  Sys.sleep(1)             # Emulate slow algorithm
  cat("ok\n")
  saveCache(data, key=key, comment="simulate()")

  data;
}

data <- simulate(2.3, 3.0)
data <- simulate(2.3, 3.5)
data <- simulate(2.3, 3.0) # Will load cached data

# Clean up
file.remove(findCache(key=list(2.3,3.0)))
file.remove(findCache(key=list(2.3,3.5)))

[Package R.cache version 0.1.7 Index]