set_default() takes a function and returns a new version with
updated default values for specified arguments.
set_default(fun, nms, vls = NULL)A function whose arguments will get new default values.
Character vector of argument names, or something coercible to that
(e.g. a call to v()).
Optional vector or list of values to use as defaults.
If nms is a named list, vls can be NULL.
A new function with updated default values in its formals.
This is useful when you want to programmatically create specialized versions of a function with certain arguments preset to default values.
The specified arguments will be moved to the end of the formal argument list in the returned function.
You can supply arguments as a named list or as separate names and values.
## Simple example
f1 <- function(x, y, z) { x + y + z }
## Add defaults for x and y
set_default(f1, list(x = 1, y = 2))
#> function (z, x = 1, y = 2)
#> {
#> x + y + z
#> }
#> <environment: 0x5e0103f85940>
# function (z, x = 1, y = 2) { x + y + z }
## Same using separate vectors of names and values
set_default(f1, c("x", "y"), c(1, 2))
#> function (z, x = 1, y = 2)
#> {
#> x + y + z
#> }
#> <environment: 0x5e0103f85940>
## Works with v() style if supported
# set_default(f1, v(x, y), c(1, 2))
## Another example with more arguments
f2 <- function(a, b, c, d) { a + b + c + d }
set_default(f2, list(b = 10, d = 5))
#> function (a, c, b = 10, d = 5)
#> {
#> a + b + c + d
#> }
#> <environment: 0x5e0103f85940>