[R] recategorizing a vector into discrete states

[Marc Schwartz (via MN)]

On Tue, 2005-08-16 at 13:18 -0400, Allan Strand wrote:
> Hi All,
> 
> I'm trying to take a numerical vector  and  produce a new vector of the 
> same length where each element in the first is placed into a category 
> given by a 'breaks-like' vector. The values in the result should equal 
> the lower bounds of each category as defined in the breaks vector.
> 
>   I suspect that a vectorized solution  is pretty simple, but I can't 
> seem to figure it out today.  Here is an example of my problem:
> 
> Vector 'a' is the original vector.  Vector 'b' gives the lower bounds 
> of the categories.  Vector 'c' is the result I am seeking.
> 
> a <- c(0.9, 11, 1.2, 2.4, 4.0, 5.0, 7.3, 8.1, 3.3, 4.5)
> b <- c(0, 2, 4, 6, 8)
> 
> c <- c(0, 8, 0, 2, 4, 4, 6, 8, 2, 4)
> 
> Any suggestions would be greatly appreciated.
> 
> cheers,
> Allan Strand

See ?cut

> a <- c(0.9, 11, 1.2, 2.4, 4.0, 5.0, 7.3, 8.1, 3.3, 4.5)
> b <- c(0, 2, 4, 6, 8)

> cut(a, c(b, Inf), labels = b, right = FALSE)
 [1] 0 8 0 2 4 4 6 8 2 4
Levels: 0 2 4 6 8

Note that cut() returns a factor.

HTH,

Marc Schwartz