[R] as.data.frame(do.call(rbind, lapply)) produces something weird

[jim holtman]

This is a case where you start by breaking down you complex one-liner
into separate statements and examine what the results are at each
point.  This is what I would have to do with the script you posted.

I think as Bill pointed out, one of your function calls is probably
creating a result that you were not expecting.  Standard (good)
programming practice would have you creating a number of simple
statements; this allows ease of debugging.

On Fri, Nov 9, 2012 at 2:21 PM, Sam Steingold <sds at gnu.org> wrote:
> The following code:
> --8<---------------cut here---------------start------------->8---
>> myfun <- function (x) list(x=x,y=x*x)
>> z <- as.data.frame(do.call(rbind,lapply(1:3,function(x) c(a=paste("a",x,sep=""),as.list(unlist(list(b=myfun(x),c=myfun(x*x*x))))))))
>> z
>    a b.x b.y c.x c.y
> 1 a1   1   1   1   1
> 2 a2   2   4   8  64
> 3 a3   3   9  27 729
> --8<---------------cut here---------------end--------------->8---
> the appearance of z is good, but str() and summary betray some weirdness:
> --8<---------------cut here---------------start------------->8---
>> str(z)
> 'data.frame':   3 obs. of  5 variables:
>  $ a  :List of 3
>   ..$ : chr "a1"
>   ..$ : chr "a2"
>   ..$ : chr "a3"
>  $ b.x:List of 3
>   ..$ : int 1
>   ..$ : int 2
>   ..$ : int 3
>  $ b.y:List of 3
>   ..$ : int 1
>   ..$ : int 4
>   ..$ : int 9
>  $ c.x:List of 3
>   ..$ : int 1
>   ..$ : int 8
>   ..$ : int 27
>  $ c.y:List of 3
>   ..$ : int 1
>   ..$ : int 64
>   ..$ : int 729
> --8<---------------cut here---------------end--------------->8---
> how do I ensure that the columns of z are vectors, as in
> --8<---------------cut here---------------start------------->8---
>> z <- data.frame(a=c("a1","a2","a3"),b.x=c(1,2,3),b.y=c(1,4,9),c.x=c(1,8,27),c.y=c(1,64,729))
>> z
>    a b.x b.y c.x c.y
> 1 a1   1   1   1   1
> 2 a2   2   4   8  64
> 3 a3   3   9  27 729
>> str(z)
> 'data.frame':   3 obs. of  5 variables:
>  $ a  : Factor w/ 3 levels "a1","a2","a3": 1 2 3
>  $ b.x: num  1 2 3
>  $ b.y: num  1 4 9
>  $ c.x: num  1 8 27
>  $ c.y: num  1 64 729
> --8<---------------cut here---------------end--------------->8---
> thanks!
>
> --
> Sam Steingold (http://sds.podval.org/) on Ubuntu 12.04 (precise) X 11.0.11103000
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>
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-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.