[R] table() of a factor

Robin Hankin rksh1 at cam.ac.uk
Tue Jun 29 12:59:18 CEST 2010


suppose I have a factor 'x':

 > x <- as.factor(c(rep("a",3),"b","d"))
 > table(x)
a b d
3 1 1

But this is not what I want because
I need to include the fact that the count of "c" is zero.

I can't just change the levels of x:

 > levels(x) <- c("a","b","c","d")
 > table(x)
a b c d
3 1 1 0

because this records the single "d" in the original 'x' as a "c".

What I want is:

a b c d
3 1 0 1

How to get this from 'x'?
(my real application has dozens of levels with complicated names).

Robin K. S. Hankin
Uncertainty Analyst
University of Cambridge
19 Silver Street
Cambridge CB3 9EP

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