Merging data frames with no by variables does not append suffixes to
column names to keep them unique. Also, shouldn't by=NULL be a
legitimate way to get the "Cartesian product" of two data frames,
instead of getting the error message "'by' must specify
columns"?
> df=data.frame(col=1:3)
> merge(df,df,by=numeric(0))
col col
1 1 1
2 2 1
3 3 1
4 1 2
5 2 2
6 3 2
7 1 3
8 2 3
9 3 3
>
> merge(df,df,by=NULL)
Error in fix.by(by.x, x) : 'by' must specify column(s)
>
> sessionInfo()
R version 2.2.1, 2005-12-20, powerpc-apple-darwin7.9.0
attached base packages:
[1] "methods" "stats" "graphics"
"grDevices" "utils"
[6] "datasets" "base"
>
> version
_
platform powerpc-apple-darwin7.9.0
arch powerpc
os darwin7.9.0
system powerpc, darwin7.9.0
status
major 2
minor 2.1
year 2005
month 12
day 20
svn rev 36812
language R
>
Best,
Todd Bailey