[R] list to data frame by rows ...

[Peter Dalgaard BSA]

Douglas Bates <bates at stat.wisc.edu> writes:

> Johann Petrak <johann at ai.univie.ac.at> writes:
> 
> > Ugh, newbie question ... :
> > 
> > I have a list of vectors of equal size, like
> >   list(c(1,2,3),c(4,5,6)) 
> > and want to convert this into a data frame row-wise:
> > 
> > 1   1 4
> > 2   2 5
> > 3   3 6
> > 
> > Whats the elegant/R-way to do this?
> 
> In general the cbind function is used to bind columns into an array.
> If you want to invoke it on a list of arguments you can use do.call to
> create the function call.  Combining these gives
> 
> > mylist <- list(c(1,2,3),c(4,5,6)) 
> > do.call("cbind", mylist)
>      [,1] [,2]
> [1,]    1    4
> [2,]    2    5
> [3,]    3    6

However, if a data frame is desired all you really need is
as.data.frame:

> l <- list(c(1,2,3),c(4,5,6))
> as.data.frame(l)
  c.1..2..3. c.4..5..6.
1          1          4
2          2          5
3          3          6

(or data.frame(l) for that matter -- there's a subtle distinction
which escapes me for the moment...)

As, seen, there's a gotcha in the generation of names (try
as.data.frame(list(rnorm(100),rnorm(100))) for a more extreme
example). It would be wiser to set the names first, as in

> names(l)<-c("V1","V2"); as.data.frame(l)
  V1 V2
1  1  4
2  2  5
3  3  6

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._