[R] Unexpected behaviour as.data.frame

[Jan van der Laan]

I use the following code to create two data.frames d1 and d2 from a list:

types  <- c("integer", "character", "double")
nlines <- 10
d1     <- as.data.frame(lapply(types, do.call, list(nlines)),  
stringsAsFactor=FALSE)
l2     <- lapply(types, do.call, list(nlines))
d2     <- as.data.frame(l2, stringsAsFactors=FALSE)

I would expect d1 and d2 to be the same, however, in d1 the second  
column is a factor while in d2 it is a character (which I would expect):

> str(d1)
'data.frame':	10 obs. of  3 variables:
  $ c.0L..0L..0L..0L..0L..0L..0L..0L..0L..0L.: int  0 0 0 0 0 0 0 0 0 0
  $ c........................................: Factor w/ 1 level "": 1  
1 1 1 1 1 1 1 1 1
  $ c.0..0..0..0..0..0..0..0..0..0.          : num  0 0 0 0 0 0 0 0 0 0
> str(d2)
'data.frame':	10 obs. of  3 variables:
  $ c.0L..0L..0L..0L..0L..0L..0L..0L..0L..0L.: int  0 0 0 0 0 0 0 0 0 0
  $ c........................................: chr  "" "" "" "" ...
  $ c.0..0..0..0..0..0..0..0..0..0.          : num  0 0 0 0 0 0 0 0 0 0


As different but related question: I use the commands above to create  
an 'empty' data.frame with specified column types and dimensions. I  
need this data.frame to pass on to my c++ routines. Is there a more  
simple/elegant way of creating this data.frame?

Regards,

Jan


PS:
I am running R on 64 bit Ubuntu 11.04:

> sessionInfo()
R version 2.12.1 (2010-12-16)
Platform: x86_64-pc-linux-gnu (64-bit)

locale:
  [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
  [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
  [5] LC_MONETARY=C              LC_MESSAGES=en_US.UTF-8
  [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
  [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base