Optimization of a function using optim

Dear Graham,

I am attempting to optimize a function I have developed using optim.

I am getting the below error message:

Error in n < 1: 'n' is missing

I suspect a function requires an argument named n, and you
didn't pass one.  Either in your objective function or in optim.
See blow example that produce a similar error:

f <- function(n) {

+    if(n <1) {
+     print("one")
+    }
+ }

f()

Error in n < 1 : 'n' is missing


Best Wishes,
-m