Dear R developers,
It would be great if you could implement the two minor code changes suggested
below, which would help processing large objects in R.
Jens Oehlschlägel
# Wish no. 1: let [.AsIs return the class AFTER subsetting, not the class of
the original object
# Wish no. 2: adjust write.csv and write.csv2 for multiple calls in chunked
writing
# Rationale no. 1: a couple of packages will return a different class than
SomeClass when subsetting with [.SomeClass
# and still need to keep the AsIs property
# Examples for classes returning different classes on subscipting are in
packages 'bit', 'ff', 'bigmemory'
# For classes where [.SomeClass will return class SomeClass, such a change will
not hurt
# Code suggestion no. 1: please use
"[.AsIs" <- function (x, i, ...){
ret <- NextMethod("[")
oldClass(ret) <- c("AsIs", oldClass(ret))
ret
}
# instead of
"[.AsIs" <- function (x, i, ...)
structure(NextMethod("["), class = class(x))
# Rationale no. 2: write.csv and write.csv2 currently enforce that a header
must be written, even with append=TRUE
# This prevents a csv file being written in chunks.
# If argument append=TRUE is used, a header should not be enforced (may be even
be forbidden)
# Code suggestion no. 2: please use
write.csv <-
function (...)
{
Call <- match.call(write.table, expand.dots = TRUE)
for (argname in c("col.names", "sep", "dec", "qmethod")) if
(!is.null(Call[[argname]]))
warning(gettextf("attempt to set '%s' ignored", argname),
domain = NA)
rn <- eval.parent(Call$row.names)
ap <- eval.parent(Call$append)
Call$col.names <- if (is.logical(ap) && ap) FALSE else {if (is.logical(rn)
&& !rn) TRUE else NA}
Call$sep <- ","
Call$dec <- "."
Call$qmethod <- "double"
Call[[1L]] <- as.name("write.table")
eval.parent(Call)
}
write.csv2 <-
function (...)
{
Call <- match.call(write.table, expand.dots = TRUE)
for (argname in c("col.names", "sep", "dec", "qmethod")) if
(!is.null(Call[[argname]]))
warning(gettextf("attempt to set '%s' ignored", argname),
domain = NA)
rn <- eval.parent(Call$row.names)
ap <- eval.parent(Call$append)
Call$col.names <- if (is.logical(ap) && ap) FALSE else {if (is.logical(rn)
&& !rn) TRUE else NA}
Call$sep <- ";"
Call$dec <- ","
Call$qmethod <- "double"
Call[[1L]] <- as.name("write.table")
eval.parent(Call)
}
# instead of
write.csv <- function (...)
{
Call <- match.call(expand.dots = TRUE)
for (argname in c("col.names", "sep", "dec", "qmethod")) if
(!is.null(Call[[argname]]))
warning(gettextf("attempt to set '%s' ignored", argname),
domain = NA)
rn <- eval.parent(Call$row.names)
Call$col.names <- if (is.logical(rn) && !rn)
TRUE
else NA
Call$sep <- ","
Call$dec <- "."
Call$qmethod <- "double"
Call[[1L]] <- as.name("write.table")
eval.parent(Call)
}
write.csv2 <-
function (...)
{
Call <- match.call(expand.dots = TRUE)
for (argname in c("col.names", "sep", "dec", "qmethod")) if
(!is.null(Call[[argname]]))
warning(gettextf("attempt to set '%s' ignored", argname),
domain = NA)
rn <- eval.parent(Call$row.names)
Call$col.names <- if (is.logical(rn) && !rn)
TRUE
else NA
Call$sep <- ";"
Call$dec <- ","
Call$qmethod <- "double"
Call[[1L]] <- as.name("write.table")
eval.parent(Call)
}
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