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### This file is part of the 'foreign' package for R.
### Functions for reading and writing files in Weka ARFF format.
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# A copy of the GNU General Public License is available at
# http://www.r-project.org/Licenses/
### <NOTE>
### String and evaluation types are enclosed by single quotes upon
### writing and enclosing single quotes are removed upon reading.
### Escaped single quotes inside single quotes may also occur.
### </NOTE>
read.arff <-
function(file)
{
## See read.table().
if(is.character(file)) {
file <- file(file, "r")
on.exit(close(file))
}
if(!inherits(file, "connection"))
stop("Argument 'file' must be a character string or connection.")
if(!isOpen(file)) {
open(file, "r")
on.exit(close(file))
}
## Get header.
col_names <- NULL
col_types <- NULL
col_dfmts <- character()
line <- readLines(file, n = 1L)
while(length(line) &&
regexpr('^[[:space:]]*@(?i)data', line, perl = TRUE) == -1L) {
if(regexpr('^[[:space:]]*@(?i)attribute', line,
perl = TRUE) > 0L) {
con <- textConnection(line)
line <- scan(con, character(), quiet = TRUE)
close(con)
if(length(line) < 3L)
stop("Invalid attribute specification.")
col_names <- c(col_names, line[2L])
if((type <- tolower(line[3L])) == "date") {
col_types <- c(col_types, "character")
col_dfmts <- c(col_dfmts,
if(length(line) > 3L)
ISO_8601_to_POSIX_datetime_format(line[4L])
else "%Y-%m-%d %H:%M:%S")
}
else if(type == "relational")
stop("Type 'relational' currently not implemented.")
else {
type <- sub("\\{.*", "factor", type)
## (Could try to preserve factor levels ...)
type <- sub("string", "character", type)
type <- sub("real", "numeric", type)
col_types <- c(col_types, type)
col_dfmts <- c(col_dfmts, NA)
}
}
line <- readLines(file, n = 1L)
}
## Test header.
if(length(line) == 0L)
stop("Missing data section.")
if(is.null(col_names))
stop("Missing attribute section.")
if(length(col_names) !=
length(grep('factor|numeric|character', col_types)))
stop("Invalid type specification.")
## Get data.
data <- read.table(file, sep = ",", na.strings = "?",
colClasses = col_types, comment.char = '%')
if(any(ind <- which(!is.na(col_dfmts))))
for(i in ind)
data[i] <- as.data.frame(strptime(data[[i]], col_dfmts[i]))
## Remove left over escapes.
for (i in seq_len(length(data)))
if (is.factor(data[[i]]))
levels(data[[i]]) <- gsub("\\\\", "", levels(data[[i]]))
names(data) <- col_names
data
}
write.arff <-
function(x, file, eol = "\n", relation = deparse(substitute(x)))
{
## See write.table().
if(file == "")
file <- stdout()
else if(is.character(file)) {
file <- file(file, "wb")
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)
## We need to quote for ourselves, as write.table() escapes the quote
## char but not the backslash. Weka seems to prefer backslash
## escapes inside single quotes, so we provide that ...
squote <- function(s) {
## Don't quote NAs.
ifelse(is.na(s), s,
sprintf("'%s'", gsub("(['\\])", "\\\\\\1", s)))
}
spquote <- function(s) {
if (length(grep("^[[:alpha:]]", s)) == 0L) s <- paste("X", s, sep="")
if (length(grep(" ", s))) s <- paste('"', s, '"', sep="")
s
}
## Write header. Quote, mangle if necessary.
text <- paste('@relation', spquote(make.names(relation)))
writeLines(text, file, sep = eol)
for (name in colnames(x)) {
## Attribute names need to start with a letter, quoted if contain spaces.
text <- paste('@attribute', spquote(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], "Date")) {
text <- paste(text, "date \"yyyy-MM-dd\"")
x[,name] <- squote(format(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)
}
## Write data.
writeLines("@data", file)
write.table(x, file = file, na = "?", sep = ",",
eol = eol, quote = FALSE, row.names = FALSE,
col.names = FALSE)
}
ISO_8601_to_POSIX_datetime_format <-
function(x)
{
## First, Weka thinks that 'yyyy' is ISO 8601 ...
x <- sub("yyyy", "%Y", x, ignore.case = TRUE)
## And it's 'DD' and not 'dd' ...
x <- sub("dd", "%d", x)
## And it's 'hh' and not 'HH' ...
x <- sub("HH", "%H", x)
## Now the real stuff.
## Is there a POSIX format string for the century component of year?
x <- sub("CCYY", "%Y", x)
x <- sub("YY", "%y", x)
x <- sub("MM", "%m", x)
x <- sub("DD", "%d", x)
x <- sub("DDD", "%j", x)
x <- sub("ww", "%U", x)
x <- sub("D", "%w", x)
x <- sub("hh", "%H", x)
x <- sub("mm", "%M", x)
x <- sub("ss", "%S", x)
## Is there a POSIX format string for fractions of seconds? [No]
x
}
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