Characters vs. factors

It seems like a recent trend in R has been to make character vectors
and factors almost equivalent (apart from the way that factors always
remember their original range).  There are a few exceptions:

shopping <- read.csv("http://spreadsheets.google.com/pub?key=tE9pXlYLwTAeiDWxL8h_viA&single=true&gid=0&range=A1%3AE37&output=csv", as.is=TRUE)
shopping$seconds <- as.numeric(as.difftime(shopping$Total.Time))
fit <- lm(seconds ~ Number.of.Items + Payment - 1, shopping,subset=-8)

It seems like a recent trend in R has been to make character vectors
and factors almost equivalent (apart from the way that factors always
remember their original range). ?There are a few exceptions:

?* summary.character != summary.factor
?* table(x, exclude = NULL) != table(factor(x), exclude=NULL) when x
includes missing values

?* strsplit on a factor

strsplit(factor(c("a", "a b")), " ")

Error in strsplit(factor(c("a", "a b")), " ") : non-character argument

?* nchar on a factor:

nchar(factor(c("abc", "d", "defgh")))

[1] 1 1 1

?* : with two character strings

"a":"b"

Error in "a":"b" : NA/NaN argument
In addition: Warning messages:
1: NAs introduced by coercion
2: NAs introduced by coercion

factor("a"):factor("b")

[1] a:b
Levels: a:b

Regards,

Hadley

--
http://had.co.nz/