[Rd] feature request: comment character in read.table?

[Peter Kleiweg]

Ben Bolker scribeva...

>
>   It was pretty straightforward.
>   I haven't tested it very extensively, and not on a Mac at all.  The only
> subtlety is skipping commented lines at the beginning of the file because
> read.table assumes that the first line (not the first non-blank line) is
> the header line if header=TRUE.
>
> read.table.c <- function(file,comment="#",debug=FALSE,...) {
>   infile <- file(file,"r")
>   tmpfile <- file()
>   cchar <- "#"
>   while (length(cline <- readLines(infile,1))>0) {
>     s <- strsplit(cline,cchar)[[1]][1]
>     if (nchar(s)>0)  { ## skip blank lines to not screw up header
>       if (debug) cat(s,"\n")
>       writeLines(s,tmpfile)
>     }
>   }
>   r <- read.table(tmpfile,...)
>   close(infile)
>   close(tmpfile)
>   r
> }

That is not very robust. What about these:

    # a comment
    1 2 3  # a comment
           # a comment
    "1" "2" "3  # not a comment"
    "# not a comment"  # a comment

Comments don't have to start at the first column, and comments
can also exist after real data. A comment char within a string
should not be taken as the start of a comment, and you also have
to take into account that the tokens delimiting a string can
vary.

-- 
Peter Kleiweg
http://www.let.rug.nl/~kleiweg/

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