An updated version of my package fancycut is on CRAN. The package has one function, fancycut(), that is more versatile than cut() for certain applications. cut() takes a numeric vector and turns it into a factor or categorical vector. It works best when they are no gaps in the intervals you have defined and when the are all either right handed or left handed. It does not like point intervals or mixed open, closed, etc. fancycut() is OK with all of this. It uses interval notation we learned in high school math which is why I like it. Here is an example

  x = -10:10,  
  SubZero = '(-Inf,0)',  
  Zero = '[0,0]',  
  Small = '(0,2]',  
  Medium = '(2,5)',  
  Large = '[5,10]', = FALSE  

This returns

[1] 'SubZero' 'SubZero' 'SubZero' 'SubZero' 'SubZero' 'SubZero' 'SubZero' 'SubZero' 'SubZero' 'SubZero' 'Zero'    'Small'   'Small'   'Medium'  'Medium' 
[16] 'Large'   'Large'   'Large'   'Large'   'Large'   'Large'  

It has other features, too, please see the help files.