On 2012-10-07 14:44, Sam Steingold wrote:
* Peter Ehlers <ruy...@hpnytnel.pn> [2012-10-07 10:03:42 -0700]:
On 2012-10-07 08:34, Sam Steingold wrote:
I know it does not look very good - using the same column names to mean
different things in different data frames, but here you go:
--8<---------------cut here---------------start------------->8---
x <- data.frame(a=c(1,2,3),b=c(4,5,6))
y <- data.frame(b=c(1,2),a=c("a","b"))
merge(x,y,by.x="a",by.y="b",all.x=TRUE,suffixes=c("","y"))
a b a
1 1 4 a
2 2 5 b
3 3 6 <NA>
Warning message:
In merge.data.frame(x, y, by.x = "a", by.y = "b", all.x = TRUE) :
column name 'a' is duplicated in the result
--8<---------------cut here---------------end--------------->8---
why is the suffixes argument ignored?
I mean, I expected that the second "a" to be "a.y".
The 'suffixes' argument refers to _non-by_ names only (as per ?merge).
yes, but "a" in "y" is _not_ a by-name.
Yes, it is.
The set of by-names is the union of names specified by by.x and by.y,
in your case: c("a", "b").
I suppose that a case could be made that ?merge does not spell that
out sufficiently explicitly.
Peter Ehlers
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