[Rd] Improvements to write.arff (PR#12574)

[Prof Brian Ripley]

Thank you, but please see the R FAQ and report facts.  We need examples of 
what goes wrong, and we will also need to document the fixes (e.g. names 
get mangled).

We do prefer patches against the actual sources (lots of comments have 
been missed in your version): the current source tarball for foreign is on 
CRAN.

On Wed, 20 Aug 2008, martin at martincmartin.com wrote:

> Full_Name: Martin C. Martin
> Version: 2.7.1
> OS: Ubuntu
> Submission from: (NULL) (75.150.115.86)
>
>
> The function write.arff, in the foreign library:
>
> - Can produce relation names with invalid characters
> - Doesn't use colnames() for attribute names when writing a matrix.
>
> Here's a better version:
>
> write.arff <- function (x, file, eol = "\n")
> {
>    if (file == "")
>        file <- stdout()
>    else if (is.character(file)) {
>        file <- file(file, "w")
>        on.exit(close(file))
>    }
>    if (!inherits(file, "connection"))
>        stop("Argument 'file' must be a character string or connection.")
>    if (!is.data.frame(x) && !is.matrix(x))
>        x <- data.frame(x)
>    squote <- function(s) {
>        ifelse(is.na(s), s, sprintf("'%s'", gsub("(['\\])", "\\\\\\1",
>            s)))
>    }
>    text <- paste('@relation "', make.names(deparse(substitute(x))), '"',
> sep='')
>    writeLines(text, file, sep = eol)
>    for (name in colnames(x)) {
>        text <- paste("@attribute", name)
>        if (is.data.frame(x) && is.factor(x[[name]])) {
>            lev <- squote(levels(x[[name]]))
>            levels(x[[name]]) <- lev
>            text <- paste(text, " {", paste(lev, collapse = ","),
>                "}", sep = "")
>        }
>        else if (is.character(x[,name])) {
>            text <- paste(text, "string")
>            x[,name] <- squote((x[,name]))
>        }
>        else if (inherits(x[,name], "POSIXt")) {
>            text <- paste(text, "date \"yyyy-MM-dd hh:mm:ss\"")
>            x[,name] <- squote(format(x[,name]))
>        }
>        else {
>            text <- paste(text, "numeric")
>        }
>        writeLines(text, file, sep = eol)
>    }
>    writeLines("@data", file)
>    write.table(x, file = file, na = "?", sep = ",", eol = eol,
>        quote = FALSE, row.names = FALSE, col.names = FALSE)
> }
>
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>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595