Create a numeric vector with names in one statement?

The setNames() function is made for this purpose. As described in Advanced R and ?setNames:

test <- setNames(c(1, 2), c("A", "B"))

...as a side note, the structure function allows you to set ALL attributes, not just names:

structure(1:10, names=letters[1:10], foo="bar", class="myclass")

Which would produce

 a  b  c  d  e  f  g  h  i  j 
 1  2  3  4  5  6  7  8  9 10 
attr(,"foo")
[1] "bar"
attr(,"class")
[1] "myclass"

How about:

 c(A = 1, B = 2)
A B 
1 2 

The convention for naming vector elements is the same as with lists:

newfunc <- function(A=1, B=2) { body}  # the parameters are an 'alist' with two items

If instead you wanted this to be a parameter that was a named vector (the sort of function that would handle arguments supplied by apply):

newfunc <- function(params =c(A=1, B=2) ) { body} # a vector wtih two elements

If instead you wanted this to be a parameter that was a named list:

newfunc <- function(params =list(A=1, B=2) ) { body} 
    # a single parameter (with two elements in a list structure