read_or_cache {dlr}

Read or Cache a File

Description

This function wraps read_or_process, specifying an app's cache directory as the target directory.

Usage

read_or_cache(
  source_path,
  appname,
  filename = construct_processed_filename(source_path),
  process_f = readRDS,
  process_args = NULL,
  read_f = readRDS,
  read_args = NULL,
  write_f = saveRDS,
  write_args = NULL,
  force_process = FALSE
)

Arguments

source_path

Character scalar; the path to the raw file. Paths starting with http://, http://, http://, or http:// will be downloaded to a temp file if the processed version is not already available.

appname

Character; the name of the application that will "own" the cache, such as the name of a package.

filename

Character; an optional filename for the cached version of the file. By default, a filename is constructed using construct_processed_filename

process_f

A function or one-sided formula to use to process the source file. source_path will be passed as the first argument to this function. Defaults to read_f.

process_args

An optional list of additional arguments to process_f.

read_f

A function or one-sided formula to use to read the processed file. target_path will be passed as the first argument to this function. Defaults to readRDS.

read_args

An optional list of additional arguments to read_f.

write_f

A function or one-sided formula to use to save the processed file. The processed object will be passed as the first argument to this function, and target_path will be passed as the second argument. Defaults to saveRDS.

write_args

An optional list of additional arguments to write_f.

force_process

A logical scalar indicating whether we should process the source file even if the target already exists. This can be particularly useful if you wish to redownload a file.

Value

The processed object.

Examples

if (interactive()) {
  austin_smoke_free <- read_or_cache(
    "https://query.data.world/s/owqxojjiphaypjmlxldsp566lck7co",
    appname = "dlr",
    process_f = read.csv
  )
  head(austin_smoke_free)
}

if (interactive()) {
  # Calling the function a second time gives the result instantly.
  austin_smoke_free <- read_or_cache(
    "https://query.data.world/s/owqxojjiphaypjmlxldsp566lck7co",
    appname = "dlr",
    process_f = read.csv
  )
  head(austin_smoke_free)
}

if (interactive()) {
  # Remove the generated file.
  unlink(
    construct_cached_file_path(
      "https://query.data.world/s/owqxojjiphaypjmlxldsp566lck7co"
    )
  )
}