[R] list to data frame by rows ...
Peter Dalgaard BSA
p.dalgaard at biostat.ku.dk
Thu May 17 16:02:08 CEST 2001
Johann Petrak <johann at ai.univie.ac.at> writes:
> The result should be e.g. a data frame like:
> A B
> 1 "x" 2
> 2 "y" 4
> Of course I would also love to hear a completely different approach
> but the requirement would be that I want to map a function over a
> list of data frames and collect multi-valued results (with different
> types) into the ROWS of a new data frame.
> I hesitate to do this with all sorts of loops since I love the
> way of R of NOT doing it with loops.
> Another issue is that I want to do this with quite a lot of
> data, so it should be efficient.
> Too long a question?
It isn't easy (and the habits that data.frame has of making character
columns into factors and trying to be helpful with column names are
not making things easier). The best I can come up with is
> cl <- 1:2
> names(cl) <- c("a","b")
x x 2
y y 4
You want to give cl a names attribute for reasons you will discover by
The crucial thing is that you want the list that as.data.frame sees to
have names, so alternatively,
> l <- lapply(1:2,function(i)sapply(result,"[[",i))
> names(l) <- c("a","b")
x x 2
y y 4
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
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