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...ditonal argument. Note that the call to optim works fine unless a hessian is requested. ## Rosenbrock Banana function, modified to take an additional argument fra <- function(x,a) { x1 <- x[1] x2 <- x[2] a * (x2 - x1 * x1)^2 + (1 - x1)^2 } grra <- function(x,a) { x1 <- x[1] x2 <- x[2] c(-4*a * x1 * (x2 - x1 * x1) - 2 * (1 - x1), 2*a * (x2 - x1 * x1)) } a <- 100 xx <- c(-2.1,1) optim(c(-1.2,1), fra, grra, method = "BFGS",a=100) # this works optim(c(-1.2,1), fra, grra, met...