Searching for antilog function

Dear R-users,

I have a basic question about how to determine the antilog of a variable.

Say I have some number, x, which is a factor of 2 such that x = 2^y. I 
want to figure out what y is, i.e. I am looking for the antilog base 2 of x.

I have found log2 in the Reference Manual. But I am struggling how to 
get the antilog of that.

Any help will be appreciated!

 > version

platform i386-pc-mingw32
arch     i386          
os       mingw32       
system   i386, mingw32 
status                 
major    1             
minor    9.1           
year     2004          
month    06            
day      21            
language R

...heather