?lapply
> z <-data.frame(a=1:3,b=letters[1:3])
> lapply(z,"[",1:2)
$a
[1] 1 2
$b
[1] a b
Levels: a b c
> data.frame(lapply(z,"[",1:2)) ## Is this not what you want?
a b
1 1 a
2 2 b
You really should spend a little more time with the docs figuring out
what R _does_ and a little less complaining about what you think R
cannot do.
-- Bert
On Thu, Aug 30, 2012 at 9:44 AM, Sam Steingold <s...@gnu.org> wrote:
>> * Sam Steingold <f...@tah.bet> [2012-08-30 08:56:17 -0400]:
>>
>> Is there a way for an apply-type function to return a data frame?
>> the closest thing I think of is
>>
>> foo <- as.data.frame(t(sapply(...)))
>> names(foo) <- c(....)
>
> alas, this has a problem of creating a "homogeneous" data frame, i.e.,
> all the columns are numbers or characters, because the function passed
> to sapply returns c(....) and
>> c(1,2,"a")
> [1] "1" "2" "a"
>
> e.g.,
> as.data.frame(t(sapply(c("a,1","b,2","c,3"),function (n)
> strsplit(n,",")[[1]])))
> V1 V2
> a,1 a 1
> b,2 b 2
> c,3 c 3
>
> 'data.frame': 3 obs. of 2 variables:
> $ V1: Factor w/ 3 levels "a","b","c": 1 2 3
> ..- attr(*, "names")= chr "a,1" "b,2" "c,3"
> $ V2: Factor w/ 3 levels "1","2","3": 1 2 3
> ..- attr(*, "names")= chr "a,1" "b,2" "c,3"
>
> I wanted the V1 column to be a string, and V2 to be a number.
> (I know stringsAsFactors=FALSE would replace factors with strings, but I
> need a string and a number)
>
> I could, of course, do ret$V2 <- as.numeric(ret$V2) but this would mean
> a double conversion: from number to string first (by c()) and then back.
>
> thanks.
>
> --
> Sam Steingold (http://sds.podval.org/) on Ubuntu 12.04 (precise) X
> 11.0.11103000
> http://www.childpsy.net/ http://mideasttruth.com http://truepeace.org
> http://openvotingconsortium.org http://ffii.org http://www.memritv.org
> Diplomacy is the art of saying "nice doggy" until you can find a nice rock.
>
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--
Bert Gunter
Genentech Nonclinical Biostatistics
Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm
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