Thanks a lot!!!
the "drop" thing was exactly what I was looking for (I already used it some
time ago but forgot about it).
Thanks to everybody else too.
Antje
Prof Brian Ripley schrieb:
On Fri, 5 Dec 2008, jim holtman wrote:
try this:
df <- data.frame(factor(c("a","a","c","b","b")), c(4,5,6,7,8),
c(9,1,2,3,4))
names(df) <- c("X1","X2","X3")
my.sub <- subset(df, X1 == "a" | X1 == "b")
levels(my.sub$X1)
[1] "a" "b" "c"
my.sub$X1 <- factor(my.sub$X1)
I find
my.sub$X1 <- my.sub$X1[drop=TRUE]
a lot more self-explanatory. See ?"[.factor". However, if you find
yourself wanting to do this, ask why you have a factor (rather than a
character vector) in the first place.
levels(my.sub$X1)
[1] "a" "b"
On Fri, Dec 5, 2008 at 7:50 AM, Antje <[EMAIL PROTECTED]> wrote:
Hello,
I hope this question is not too stupid. I would like to know how to
update
levels after subsetting data from a data.frame.
df <- data.frame(factor(c("a","a","c","b","b")), c(4,5,6,7,8),
c(9,1,2,3,4))
names(df) <- c("X1","X2","X3")
my.sub <- subset(df, X1 == "a" | X1 == "b")
levels(my.sub$X1)
# still gives me "a","b","c", though the subset does not contain entries
with "c" anymore
I guess, the solution is rather simple, but I cannot find it.
Antje
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Jim Holtman
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What is the problem that you are trying to solve?
______________________________________________
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PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
