R help - Mar 2010 - rbind, data.frame, classes

Hi,

This has bugged me for a bit. First question is how to keep classes with
rbind, and second question is how to properly return vecotrs instead of
lists after turning an rbind of lists into a data.frame

list1=list(a=2, b=as.Date("20090102", format="%Y%m%d"))
list2=list(a=2, b=as.Date("20090102", format="%Y%m%d"))

rbind(list1, list2) #this loses the posixct class. My first question is is
there a way to do this without losing the classes?

data.frame(rbind(list1, list2))
data.frame(rbind(list1, list2))$a #this returns a list output  and not a
vector output. (this is a huge pain)
data.frame(rbind(list1, list2))[,c("a")] #also returns list output

#> data.frame(rbind(list1, list2))[,c("a")]
#$list1
#[1] 1
#
#$list2
#[1] 2

# I would instead like [1] 1 2 like in the below example
> vec1 = c(1,2)
> vec2 = c(2,3)
> data.frame(rbind(vec1, vec2))[,1] #this outputs as a vector which is what
I want from the above list rbind.

is it possible to easily do the above? I read over rbind but it doesn't seem
to have any of the above fixes. Is there a different function that does this
the way I want it to?

Thanks,
Rob

	[[alternative HTML version deleted]]

Try this:

do.call(rbind, lapply(list(list1, list2), as.data.frame))

On Mon, Mar 15, 2010 at 3:42 PM, Rob Forler <rforler at uchicago.edu>
wrote:
> Hi,
>
> This has bugged me for a bit. First question is how to keep classes with
> rbind, and second question is how to properly return vecotrs instead of
> lists after turning an rbind of lists into a data.frame
>
> list1=list(a=2, b=as.Date("20090102", format="%Y%m%d"))
> list2=list(a=2, b=as.Date("20090102", format="%Y%m%d"))
>
> rbind(list1, list2) #this loses the posixct class. My first question is is
> there a way to do this without losing the classes?
>
> data.frame(rbind(list1, list2))
> data.frame(rbind(list1, list2))$a #this returns a list output ?and not a
> vector output. (this is a huge pain)
> data.frame(rbind(list1, list2))[,c("a")] #also returns list
output
>
> #> data.frame(rbind(list1, list2))[,c("a")]
> #$list1
> #[1] 1
> #
> #$list2
> #[1] 2
>
> # I would instead like [1] 1 2 like in the below example
>
>> vec1 = c(1,2)
>> vec2 = c(2,3)
>> data.frame(rbind(vec1, vec2))[,1] #this outputs as a vector which is
what
> I want from the above list rbind.
>
> is it possible to easily do the above? I read over rbind but it doesn't
seem
> to have any of the above fixes. Is there a different function that does
this
> the way I want it to?
>
> Thanks,
> Rob
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
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>


-- 
Henrique Dallazuanna
Curitiba-Paran?-Brasil
25? 25' 40" S 49? 16' 22" O