r - Minimum value of function

Question

How can I find out the minimum value that can be returned by a function with infinite domain in R?

f <- function(x) { x^2-1 }
print(minVal(f))   # -1

f <- function(x) { x^2+1 }
print(minVal(f))   # 1

So far I've tried optimize, but it requires a finite interval:

minVal <- function(f) {
  optimize(f, c(-100, 100))
}

question from:https://stackoverflow.com/questions/65851631/minimum-value-of-function

Answer 1

Have you tried the nlm function?

nlm(function(x) x^2 -1, p = 1E3)

$minimum
[1] -1

$estimate
[1] -2.499974e-10

$gradient
[1] 9.995338e-07

$code
[1] 1

$iterations
[1] 1

p is a starting value for minimization that is required.