Behaviour of read.table with empty columns
Perhaps this has to do with the fact that there is not enough
information available
to establish the class of those columns. For example, try this:
read.table("clipboard", colClasses = "character")
On 5/9/07, John Fox <jfox at mcmaster.ca> wrote:
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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