[R] Levels in returned data.frame after subset

[Ulrik Stervbo]

Thanks for the replies!  Obviously I must have used to wrong search
terms - sorry.

@greg: I care about the levels after the subset, because if they are
not dropped, then they still appear in the subsequent heatmap I make
with ggplot (with my read data-set of course). Admittedly I am quite
green, and may do things in a rather silly way - but it works (at
least I think it does)



On 4 September 2010 15:41, Ista Zahn <izahn at psych.rochester.edu> wrote:
> Hi Ulrik
>
> On Sat, Sep 4, 2010 at 12:52 PM, Ulrik Stervbo <ulrik.stervbo at gmail.com> wrote:
>> Dear List,
>>
>> When I subset a data.frame, the levels are not re-adjusted (see
>> example). Why is this? Am I missing out on some basic stuff here?
>
> Only that this issue has come up many times before, and that this list
> is archived and searchable. Try
>
> RSiteSearch("subset drop levels", restrict = c("Rhelp10", "Rhelp08", "Rhelp02"))
>
>
> -Ista
>
>>
>> Thanks
>> Ulrik
>>
>>
>>> m <- data.frame(gender = c("M", "M","F"), ht = c(172, 186.5, 165), wt = c(91,99, 74))
>>> dim(m)
>> [1] 3 3
>>
>>> levels(m$gender)
>> [1] "F" "M"
>>
>>> s <- subset(m, m$gender == "M")
>>> dim(s)
>> [1] 2 3
>>
>>> levels(s$gender)
>> [1] "F" "M"
>>
>>> cat <- sapply(s, is.factor); s[cat] <- lapply(s[cat], factor)
>>> dim(s)
>> [1] 2 3
>>
>>> levels(s$gender)
>> [1] "M"
>>
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>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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>>
>
>
>
> --
> Ista Zahn
> Graduate student
> University of Rochester
> Department of Clinical and Social Psychology
> http://yourpsyche.org
>