[Rd] row.names in data.frame with row.names NULL

Vadim Organovich vogranovich at jumptrading.com
Wed Aug 20 22:26:54 CEST 2008

Dear R-devel,

It appears that data.frame ignores row.names=NULL argument if it can guess the names from the first column. This behavior seems to contradict what the help page says, see the last sentence:

     If row names are not supplied in the call to 'data.frame', the row
     names are taken from the first component that has suitable names,
     for example a named vector or a matrix with rownames or a data
     frame. (If that component is subsequently recycled, the names are
     discarded with a warning.)  If 'row.names' was supplied as 'NULL'
     or no suitable component was found the row names are the integer
     sequence starting at one (and such row names are considered to be
     'automatic', and not preserved by 'as.matrix').

Probably it should read "AND no suitable component was found ...", but I like the promise of the original description better.


> row.names(data.frame(x=c(a=1,b=2), row.names=NULL))
[1] "a" "b"
> version
platform       i386-pc-mingw32
arch           i386
os             mingw32
system         i386, mingw32
major          2
minor          7.1
year           2008
month          06
day            23
svn rev        45970
language       R
version.string R version 2.7.1 (2008-06-23)

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