Collapse factor levels

Kevin E. Thorpe wrote:

I'm sure this is simple enough, but an R site search on my subject
terms did suggest a solution.  I have a numeric vector with many
values that I wish to create a factor from having only a few levels.
Here is a toy example.

 > x <- 1:10
 > x <- 

factor(x,levels=1:10,labels=c("A","A","A","B","B","B","C","C","C","C"))

 > x

 [1] A A A B B B C C C C
Levels: A A A B B B C C C C

 > summary(x)

A A A B B B C C C C
3 0 0 3 0 0 4 0 0 0

So, there are clearly still 10 underlying levels.  The results I would
like to see from printing the value and summary(x) are:

 > x

 [1] A A A B B B C C C C
Levels: A B C

 > summary(x)

A B C
3 3 4

Hopefully this makes sense.

Thanks,

Kevin

It's an anomaly inherited frokm S-PLUS (or so I have been told). 
Actually, with the current R, you should get a warning:

 > x <- 1:10
 > x <- 

factor(x,levels=1:10,labels=c("A","A","A","B","B","B","C","C","C","C"))
Warning message:
In `levels<-`(`*tmp*`, value = c("A", "A", "A", "B", "B", "B", "C",  :
  duplicated levels will not be allowed in factors anymore

This works (as documented on the help page for levels!):

 > x <- 1:10
 > x <- factor(x,levels=1:10)
 > levels(x) <- c("A","A","A","B","B","B","C","C","C","C")
 > table(x)

x
A B C
3 3 4