set: Assign values only when needed
In pkgutils: Utilities for Creating R Packages

Description Usage Arguments Details Value See Also Examples

A helper function for avoiding long-running computations if the object to be generated is either already present or can be read from an Rda file.

1 2	set(name, expr, template = "%s.Rda", env = parent.frame(), inherits = TRUE)

`name`	Character scalar indicating the name of an object to be assigned.
`expr`	Expression that will only be evaluated if `name` does not yet exist and, optionally, cannot be read from an `Rda` file.
`template`	Character scalar with a template as used by `sprintf` from the base package, with the placeholder, if any, referring to `name`. Set this to an empty object to turn of the `Rda` file mechanism.
`env`	Passed as `envir` argument to `assign`.
`inherits`	Passed as `inherits` argument to `assign`.

If the Rda file name has no directory component, it is assumed to be located in the directory given by getOption("rda_store") and, if this does not exist, in the directory given by getwd().

An invisible returned integer code indicating what has been done.

0: The object already existed, nothing was done.
1: The result of expr was assigned to the object, the Rda file mechanism was not used.
2: The given Rda file was found and its content assigned to the object.
3: The given Rda file was not found. The result of expr was assigned to the object and was also stored in the given Rda file.

base::assign base::readRDS base::saveRDS

Other coding-functions: L, LL, assert, case, check, collect, contains, flatten, listing, map_names, map_values, must, sql, unnest

the_answer <- function() {
  print("answer requested")
  42L
}
set("answer", the_answer(), NULL) # prints 'answer requested'
set("answer", the_answer(), NULL) # does not print
answer # 42