Defaults: Manage Default Argument Values for quantmod Functions

In quantmod: Quantitative Financial Modelling Framework

Manage Default Argument Values for quantmod Functions

Description

Use globally specified defaults, if set, in place of formally specified default argument values. Allows user to specify function defaults different than formally supplied values, e.g. to change poorly performing defaults, or satisfy a different preference.

Usage

setDefaults(name, ...)
unsetDefaults(name, confirm = TRUE)
getDefaults(name = NULL, arg = NULL)
importDefaults(calling.fun)

Arguments

name	name of function, quoted or unquoted (see Details)
...	name=value default pairs
confirm	prompt before unsetting defaults
arg	values to retrieve
calling.fun	name of function to act upon

Details

setDefaults

Provides a wrapper to R options that allows the user to specify any name=value pair for a function's formal arguments. Only formal name=value pairs specified will be updated.

Values do not have to be respecified in subsequent calls to setDefaults, so it is possible to add new defaults for each function one at a time, without having to retype all previous values. Assigning NULL to any argument will remove the argument from the defaults list.

name can be an unquoted, bare symbol only at the top-level. It must be a quoted character string if you call setDefaults inside a function.

unsetDefaults

Removes name=value pairs from the defaults list.

getDefaults

Provides access to the stored user defaults. Single arguments need not be quoted, multiple arguments must be in a character vector.

importDefaults

A call to importDefaults should be placed on the first line in the body of the function. It checks the user's environment for globally specified default values for the called function. These defaults can be specified by the user with a call to setDefaults, and will override any default formal parameters, in effect replacing the original defaults with user supplied values instead. Any user-specified values in the parent function (that is, the function containing importDefaults) will override the values set in the global default environment.

Value

setDefaults	None. Used for it's side effect of setting a list of default arguments by function.
unsetDefaults	None. Used for it's side effect of unsetting default arguments by function.
getDefaults	A named list of defaults and associated values, similar to formals, but only returning values set by setDefaults for the name function. Calling getDefaults() (without arguments) returns in a character vector of all functions currently having defaults set (by setDefaults). This does not imply that the returned function names are able to accept defaults (via importDefaults), rather that they have been set to store user defaults. All values can also be viewed with a call to getOption(name_of_function.Default).
importDefaults	None. Used for its side-effect of loading all non-NULL user- specified default values into the current function's environment, effectively changing the default values passed in the parent function call. Like formally defined defaults in the function definition, default values set by importDefaults take lower precedence than arguments specified by the user in the function call.

Note

setDefaults

At present it is not possible to specify NULL as a replacement for a non-NULL default, as the process interprets NULL values as being not set, and will simply use the value specified formally in the function. If NULL is what is desired, it is necessary to include this in the function call itself.

Any arguments included in the actual function call will take precedence over setDefaults values, as well as the standard formal function values. This conforms to the current user experience in R.

Like options, default settings are not kept across sessions. Currently, it is not possible to pass values for ... arguments, only formally specified arguments in the original function definition.

unsetDefaults

unsetDefaults removes the all entries from the options lists for the specified function. To remove single function default values simply set the name of the argument to NULL in setDefaults.

importDefaults

When a function implements importDefaults, non-named arguments may be ignored if a global default has been set (i.e. not NULL). If this is the case, simply name the arguments in the calling function.

This should also work for functions retrieving formal parameter values from options, as it assigns a value to the parameter in a way that looks like it was passed in the function call. So any check on options would presumably disregard importDefaults values if an argument was passed to the function.

Author(s)

Jeffrey A. Ryan

See Also

options

Examples

my.fun <- function(x=3)
{
  importDefaults('my.fun')
  x^2
}

my.fun()        # returns 9

setDefaults(my.fun, x=10)
my.fun()        # returns 100
my.fun(x=4)     # returns 16

getDefaults(my.fun)
formals(my.fun)
unsetDefaults(my.fun, confirm=FALSE)
getDefaults(my.fun)

my.fun()        # returns 9

quantmod documentation built on May 29, 2024, 8:03 a.m.