Named parameters in optim()

If I name the elements of the vector of initial values passed to
optim(), then it attaches the names to the final result, e.g.

f <- function(parms) (parms[1]-1)^2+(parms[2]-2)^2
optim(c(x=3,y=4), f)

$par
        x         y
0.9999635 2.0003241

$value
[1] 1.063637e-07

$counts
function gradient
      65       NA

$convergence
[1] 0

$message
NULL

However, the vector that gets passed to f doesn't have its names attached:

f <- function(parms) {

+  print(parms)
+  (parms["x"]-1)^2+(parms["y"]-2)^2
+ }

optim(c(x=3,y=4), f)

[1] 3 4
Error in optim(c(x = 3, y = 4), f) : function cannot be evaluated at
initial parameters

Is this something that should be fixed, i.e. could it be fixed without
making optim() substantially slower?  If not, it's at least something
that should be documented.

Duncan Murdoch

I think the cost is small, and have just added this.

On Thu, 2 Mar 2006, Duncan Murdoch wrote:

If I name the elements of the vector of initial values passed to
optim(), then it attaches the names to the final result, e.g.

f <- function(parms) (parms[1]-1)^2+(parms[2]-2)^2
optim(c(x=3,y=4), f)

$par
        x         y
0.9999635 2.0003241

$value
[1] 1.063637e-07

$counts
function gradient
      65       NA

$convergence
[1] 0

$message
NULL

However, the vector that gets passed to f doesn't have its names attached:

f <- function(parms) {

+  print(parms)
+  (parms["x"]-1)^2+(parms["y"]-2)^2
+ }

optim(c(x=3,y=4), f)

[1] 3 4
Error in optim(c(x = 3, y = 4), f) : function cannot be evaluated at
initial parameters

Is this something that should be fixed, i.e. could it be fixed without
making optim() substantially slower?  If not, it's at least something
that should be documented.

Duncan Murdoch