Dear r-devel list members,
I stumbled across the following behaviour of read.table() recently: Suppose
that I have the data
a " " ""
"" "" ""
in a file or copied to the clipboard, and issue the command
> DF <- read.table("clipboard")
> DF
V1 V2 V3
1 a NA NA
2 NA NA
> is.na(DF)
V1 V2 V3
[1,] FALSE TRUE TRUE
[2,] FALSE TRUE TRUE
I was surprised by the NAs. Note that they occur only when a column consists
entirely of empty strings or strings composed of blanks.
On the other hand
> data.frame(A=c("", "", ""))
A
1
2
3
works as I would have expected.
A work-around for me was
> DF[is.na(DF)] <- ""
> DF
V1 V2 V3
1 a
2
But, as I said, I found the behaviour of read.table() puzzling.
All this is with R 2.5.0 on a Windows XP Pro SP 2 system.
Comments?
Thanks,
John
--------------------------------
John Fox, Professor
Department of Sociology
McMaster University
Hamilton, Ontario
Canada L8S 4M4
905-525-9140x23604
http://socserv.mcmaster.ca/jfox
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