Hello,
When I merge two dataframes, each created by read.table and containing no
factors, the result has columns which have been converted to factor. I think
this is a bug (and may be related to some fixed bugs, eg PR#1102, PR#1121), but
will await comments before submitting. Also, I'm not sure if the bug is in
merge() or in read.table(). I am using R-1.4.0 patch 1/13/02 on Solaris 2.6.
File "merge1.txt":
k a
A w
B x
File "merge2.txt":
k b
A y
C z
Bug-testing code:
R> x <-
read.table("merge1.txt",header=T,row.names=NULL,colClasses="character")
R> y <-
read.table("merge2.txt",header=T,row.names=NULL,colClasses="character")
R> z <- merge(x, y, all.x=T)
R> sapply(z, is.factor)
k a b
FALSE FALSE TRUE
Note z$b has become a factor! I strongly suspect it has to do with setting
all.x=T and the fact that some rows of z$b (for key k="B") had to be
filled in.
Also note, I do not get this behavior if I create "x" and
"y" with data.frame:
R> x <- data.frame(k=I(c("A","B")),
a=I(c("w","x")))
R> y <- data.frame(k=I(c("A","C")),
b=I(c("y","z")))
R> z <- merge(x, y, all.x=T)
R> sapply(z, is.factor)
k a b
FALSE FALSE FALSE
Version:
platform = sparc-sun-solaris2.6
arch = sparc
os = solaris2.6
system = sparc, solaris2.6
status = Patched
major = 1
minor = 4.0
year = 2002
month = 01
day = 13
language = R
Search Path:
.GlobalEnv, package:secref, package:misc, package:io, package:arrays,
package:ls1, package:g.data, package:db, package:ts, package:ctest, Autoloads,
package:base
--
-- David Brahm (brahm at alum.mit.edu)
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