NEG {mvbutils}

Generate a negated version of your function. Useful for 'nlminb' etc.

Description

You pass it a function f(.); it returns a function whose result will be -f(.). The arguments, return attributes, and environment are identical to those of f.

Usage

NEG(f)

Arguments

f

Normally, a function that returns a scalar; rarely, a NULL.

Value

A function that returns -f. However, if is.null(f), the result is also NULL; this is useful e.g. for gradient arg to nlminb.

Examples

NEG( sqrt)( 4) # -2
# should put in more complex one here...
e <- new.env()
e$const <- 3
funco <- function( x) -sum( ( x-const)^2L)
environment( funco) <- e
nlminb( c( 0, 0), NEG( funco)) # c( 3, 3)
dfunco <- NULL
nlminb( c( 0, 0), NEG( funco), gradient=NEG( dfunco)) # c( 3, 3)