[R] Categories or clusters for univariate data

[Allen Hathaway]

If I have a vector, x, such that

x <- c(1,2,3,4,5,8,9,10,11,12,15,16,17,18,19,22,23,24,33,34,35)

if I plot that vector

plot(x)

it is visibly obvious that the data "groups" or "clusters" into distinct 
groupings.  The data trends along a more-or-less linear path, and then an 
abrupt jump.  For a trivial case, such as I have given, you can pick out the 
groups or categories visually, and manually derive the upper and lower 
bounds for each group.  My question is, is there a function in R that can do 
the same thing for more complex and subtle groupings in univariate data, and 
provide a statistical basis for the result?

Allen