[R] From data frame to list object

[David Winsemius]

On Jan 31, 2011, at 1:03 PM, Bogaso Christofer wrote:

> Dear all, let say I have following data frame:
>
>

 > dfrm <- data.frame(x=rnorm(18), y=rep(c("a", "b", "c"), each=6))
 > tapply(dfrm$x, dfrm$y, c)
$a
[1]  0.9711995  1.4018345 -1.4355713 -0.5106138 -0.8470171
[6]  1.1634586

$b
[1] -0.8058164  0.4977112  1.1556391  0.8158588  0.2549273
[6]  3.0758260

$c
[1]  0.437345128 -0.415874363  0.003230285 -0.737117910
[5]  1.247972964  0.903001077


>
>> data.frame(x=rnorm(18), y=rep(c("a", "b", "c"), each=6))
>
>              x y
>
> 1  -1.072152537 a
>
> 2   0.382985265 a
>
> 3   0.058877377 a
>
> 4  -0.006911939 a
>
> 5  -2.355269051 a
>
> 6  -0.303095553 a
>
> 7   0.484038422 b
>
> 8   0.733928931 b
>
> 9  -1.136014346 b
>
> 10  0.503552090 b
>
> 11  1.708609658 b
>
> 12 -0.294599403 b
>
> 13  1.239308497 c
>
> 14  0.754081946 c
>
> 15 -0.237346858 c
>
> 16 -0.051011439 c
>
> 17 -0.618675146 c
>
> 18  0.537612359 c
>
>
>
>> From this data frame I want to create a "list" of length 3, where  
>> each
> element of this list will be a vector corresponding to the value of  
> y. For
> example, 1st element will be all "x" values corresponding to the  
> "y=a", and
> similarly the other elements of this list. Can somebody point me how  
> to do
> this without having some "for" loop?
>
>
>
> Thanks and regards,
>
>
> 	[[alternative HTML version deleted]]
>
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David Winsemius, MD
West Hartford, CT